The FDA does a lot of stuff that is great, but the institutional paranoia about someone, somewhere being able to recreationally consume alcohol isn't one of them.
That said, I won't claim to know precisely where the line should be drawn, but would say that in a sanitizing product shortage during a pandemic the line should be somewhere in the area of "hey how about we make it easier to make more sanitizing products right now"
In particular, you can spin robitussin rapidly to separate the dextromethorphan.
I think if the alcoholic nature of extracts were more widely known to teenagers, more would take advantage. But it also doesn't come in a convenient "party" format. If you could walk into Walmart, buy a half-gallon of sanitizer for $10 (well, pre-covid you could get those sizes for cheap, now not so much) and mix it with a gallon of fruit punch, then you've basically got the ingredients for a typical small 4-8 person Everclear & Fruitpunch highschool basement party without the hassle of tracking down that >= 21 friend.