Hi tfunder,
welcome to this Apple (user-to-user) Community!
Re: "Assistive access problem"
on an iphone xs I have to tap three times on the screen to enter the phone after standby,
on an iphone 16 pro i only have to tap once to enter the phone after standby. Why?"
Am no expert in this area, yet your request deserves some response.
Wondering whether or not the two iPhones have the same iOS version installed ?
If not, it is likely some features will just work differently, as updates do often introduce improvements.
If you want: You can check each iPhone's version in Settings > General > About.
or
You can just check each iPhone to see if an update is available in Settings > General > Software updates
The newest iOS version : About iOS 18 Updates - Apple Support says iOS 18.5 is the latest
Also says: "This update introduces ... features, bug fixes, and security updates for your iPhone"
NB: If you want to install the newest version on one, or both iPhones, it is always wise to back-up iPhone first
All the best :-)