> I don't think it matters whether it is SA or NSA, the end user doesn't know the difference, the important thing is to see if there is an improvement

It does. It could be a hardware issue (need a new phone), software issue (e.g. OS support) or even configuration. It might not be turned on by default. I've also seen implementations where old physical sims needed be replaced.

> the study simply tries to understand if there is an improvement between the 5G and 4G label on the phone

Which misses a lot, e.g. modem changes on newer phones and bands supported, etc. As people keep buying new phones things will change.