Oh, I don't know about that statement.
For all the times that I have witnessed people struggling to put their poncho on, particularly when it is windy, with it getting caught on their head and backpack and they need someone else to help them pull it down so it covers their backpack and help them to secure the sides.
And for all the times I've witnessed people with ponchos on struggle to get them off, arms swinging wildly in a bar as they struggle, with one person we saw almost panicked like they were stuck in a dark, scary space with it half on/half off (we had to get up and help them remove it before they really got panicked!), and the sweat that I've seen people dripping from being stuck inside that poncho, I'm not convinced it's the right solution.
I'll keep using my jacket as rain protection as I have for nearly 60 years. It's worked very well for me and has been very convenient to put on, open pit zips to cool, and easily to remove.
Besides, don't you have to take off your pack to get to the poncho stored within in order to put it on?