Most recent version show the world's version in quit visible red font so unless you do not pay attention this isn't rly an issue.
Also just to be sure i was not missing something...
I do not know in which version it lost this ability but (atleast with 1.16.1) YOU CANNOT USE mods/1.16.1/*mods* anymore
So the quick F.A.Q on the "Read first" post is a bit outdated.
What i understand from your reply is it's just double edge sword, there will always be draw back if not used correctly. (RE)adding this feature has no draw back however. It's up to the user to still split every game version and waste ton of hard drive space.
Some version of minecraft has the same option.exe layout, so making let's say 1.14.4 & 1.15.2 into the same game directory wont be an issue for the game setting.