There have also been rumors that some parts would not be replaceable unless you used original parts but I have never had any problems with “original” parts (eg refurb screen with new 3rd party glass), obviously if a phone required parts one could not buy it can’t be considered user serviceable at all.
https://www.macrumors.com/2018/08/14/inside-the-iphone-repai...
They have tried to pull this stunt multiple times already. But have been forced to revert due to the amount of negative press it was getting. It's astounding that they tried it more than once.
I know that modifies the engineering (aka, the phone must be thicker) but it's not clear to me that there's much a of a real benefit to a phone being especially thin?
Over the lifespan (ownership) of e.g 3 years I usually replace the screen at least once, usually also some other component. Having the battery user replaceable wouldn’t make much difference, it would be 2 services instead of 3 in case the battery died.
I never replaced a battery on any of my 3 smartphones nor on any of the 4 dumbphones before them.
The only part that is using any significant adhesive is the battery, it can’t be fit because it needs to be able to grow, so it is fit into a too large space using a piece of adhesive tape to not move around.
The phone is built to be quickly servicable by Apple technicians, so obviously no cables are soldered, everything is using easy to fit ribbon connectors.
I’d have no training and found it easy to replace many parts in iPhones such as e.g the screen.
There are parts that Apple have made harder to user replace such as the fingerprint/home button module but that at least has good reason.
I recommend the ifixit step by step repair guides that also make it obvious that repairing a modern smartphone is not much different if it says google or Apple or Samsung on the back. The only major difference is a user accessible battery in some models.