I think this is the most important aspect of this thread. Not only am I seeing normal cycle counts for the degradation displayed, but they also aren’t even below 80%. And this is discounting the fact that battery health will never be relevant on the original iOS version regardless of percentage (which the 14 series cannot be updated from, yet).
Besides, I find one of our previous conversations very relevant: we had stated that heavy users exhibit a better cycle-to-health ratio because time isn’t as significant of a factor, so that coupled to what you said should end up giving the usually good results regardless of the current situation (and not that 90% health after over 300 cycles is poor in any way).
Using the following post as an example:
Around 91% after 321 cycles on the original version of iOS has no effect on battery life, and it may stabilise around this point, staying at that health for hundreds of cycles if used moderately heavily.