(Mind you on mobile I very much don't have a perfectly good window manager, and indeed can't even open multiple instances of most apps…)
Why would anyone encourage building such a tool, I can't fathom.
The OTP is the same for a user across rides, so I have mine memorised which is nifty. No fiddling with the phone during boarding.
On security: exploiting this would require the driver to stay in my vicinity the next time I book a ride, and also get the ride assigned to them. In a high population density area, it's rare - I've never had the same driver twice.
OTPs are a simple solution to fraudulent rides that it's surprising it's not implemented universally, given all the complaints in this thread.