I’d say that you do your journey how you see fit and if you visit the places where stamps can be given before and after your bus journey, and it feels right & fun, then go for it! If you are doing it for spiritual or religious reasons then meditate/pray about it and see what the right answer is for you.
Some people start their journey wayyyy beyond Logroño, some people go by bike, some go parts by car due to injury etc, so there is no answer that is ‘the right answer’. This is your pilgrimage. If a bus journey and stamps are part of your journey, absolutely go for it. If you think it would not feel authentic or whatever else, then don’t. I think the main protocol is that no one can dictate what your pilgrimage means to you and how to shape it for you.
Have a good journey and Ultreia!