Ok, that's how it is on my Samsung now. I use Nova Launcher for the double tap to sleepsorry, double tap works to wake the screen, but not to sleep.
Just found there are a few apps available as a workaround, like this one:
I now have a transparent widget on my homescreen and a button in the quick settings, pull down.One Click Lock Screen - Apps on Google Play
Simple app to lock the screen, it also supports unlocking with fingerprint.play.google.com
They do require the accessibility permission though.