A standard pinball flipper button will screw into the same position if an owner wishes to change them. There might be an issue with the button illumination PCB but it isn't required for normal operation of the machine.
Our buttons are an almost exact replica of a standard pinball flipper button. Our plastic mould was made using a standard button as a guide.
There is indeed a slight depth difference but so minor that I couldn't measure it accurately.
We actually improved on the originals by adding a circlip so the button cannot fall out - this has been reported as a very common problem with a major brand that does not have a circlip and their flipper buttons fall out during a game it's reported.
"Teacups and storms therein" come to mind. Some people will look for anything to complain about I have found. There certainly are some things we can do better but complaining about these buttons is pretty petty in my view and mostly done by those clutching at straws and looking for anything to discredit our efforts.
Those who have actually bought machines report to me that they are happy.