True, but this was an aesthetic issue (antenna bands, glass exterior...). Fingerprint reader on the back on the other hand is a major usability issue (handling the phone, having a case, unlocking the phone while on the table...).
Personally I would say I unlock the phone at least 25% of the time while it's flat on the table. With every touchid iteration Apple was trying to make the unlocking faster and more seamless. Now we have raise to wake + touchid - no physical buttons, people were actually complaining that it is too fast. Now try to imagine how long it takes to do it with the reader in the back.
This is why I hope these renders are fake.