So oddly, the US was far more permissive than other locales in this one aspect. All this change does is bring it in line with security practices that other nations already had in place.
Honestly am quite surprised that the US didn’t already have this restriction considering overall it’s one of the toughest countries to get a visa for or even enter with a valid visa.
The US visa vetting procedure is known to be so strict even for tourists that many nations give visa free access to nationals who would otherwise require a visa - just because they hold a valid (or sometimes even expired!) US visa. It’s a highly regarded sticker if you can get one in your passport and seriously ups the power of your passport if it’s a weaker one to start with.