(but how many really do test their gear properly first. The amount of gear that seems to be left behind, suggests many don't).
That question is not important. We do not base advice to others on this Forum based on worst outcomes, but on how to AVOID worst outcomes. What is important is relating to others what the best practices are, and in that regard what the best practices are is matched by what this Forum encourages beginners to do.
I'm just stating that as the title of the thread suggests you could buy everything you need in St Jean if you arrived without anything, as the variety of shops is enough to be able to kit yourself out with decent quality gear to walk.
Yes, one could buy everything they needed. . . and I gave reasons why that would be a poor practice to do.
I think if I was a beginner then I could become overloaded with too much information and possibly think that I had to have the latest often expensive technical gear to be able to walk to Santiago, when many would probably already have footwear, clothing, and even possibly waterproofs and rucksack that would be suitable and already tested and be better than buying new.
I disagree. Too much information? I read just the opposite. . beginners seem to be craving to find as much information as possible. Gear and clothing discussions on the Forum are far too broad, and have far too many views offered for me to believe that a beginner would be mindlessly driven to think that they can only walk a Camino with the most expensive, and latest, most technically advanced gear.
Too much information? Well that addresses the concern you also voice that the varieties and variations of gear and clothing is covered as to what works for a wide variety of conditions, and for a wide variety of people.
Latest and greatest technical gear? It is important that folks understand the possibilities of what choices are available. Some of that gear can be expensive, which is why most of us balance such information with caveats to consider budget vs long term use.
Is the Frogg Toggs poncho or rain jacket too expensive at 15 to 20 Euro? It is one of the best technical pieces of raingear I've tested, and yet it's budget would be suitable for most. It is certainly more affordable than other commonly voiced options.
It is also a bit of a straw man to mix the subjects of using new gear vs used gear, the cost of bleeding edge gear, and when is the best time for purchasing gear before the Camino. These are completely individual topics.
ALL of my gear on Camino and most backpacking trips is used. Being 'used' means that I have had time to assess it, and to know that it works for me. So if someone is using 'used' gear that they already have, I am never going to argue that someone should replace serviceable gear or clothing with brand new gear.
The only time I have read of anyone offering different advice, is if it is in response to someone asking if there is a need to replace equipment that they think is too heavy or too worn. The biggest concern I have is that there are periodic arguments, in which someone asserts a belief that a backpack can be too big to use on Camino. There are beginners who have read this, and have then decided that they need to get a different backpack.
I frequently point out the fallacy of such arguments, and point out that buying a special Camino-sized pack is a waste of money. However, if the issue is that someone wishes to replace a worn backpack, or a heavier backpack, then I will gladly point out those options.
Many beginners do not own basic backpacking gear to use on Camino. . . no backpacks, no sleeping gear, no adequate footwear for long hikes or walks. In these cases, discussions will tend to focus on their requests for gear purchasing advice. Many times, borrowing a friend or relative's gear is mentioned as an option, and the advice for getting a proper fit and testing out such gear for comfort and usability applies, just as if the gear is new.
Talking about the latest and greatest gear is going to be a part of many threads and posts surrounding discussions about equipment. Talking about the alternative options available, for the most expensive choices of gear, will also enter the discussion and does seem to be the majority focus whenever equipment and clothing is discussed. Folks are smart enough to sort through the information and choose what is best for their needs and budget. It is not the role of the Forum to be a nanny, and decide for others exactly how much money should be spent on gear or clothing.
It seems to me that the role of this Forum is to provide a range of 'Best Practices' which will help assure a beginner's success at meeting whatever goals for a Camino that they have set for themselves. Knowing that a worn out bit of gear or clothing can be replaced while on Camino is part of that essential knowledge, as the OP focused on. It helps to overcome the need to add the extra weight of 'packing fears and just in case items'.
That is a different issue, I think, than the point of this discussion.