Personally, I wasn't a massive fan of growing in bazaar or business shops, especially big numbers growing in shops. Baring in mind everything I say here is quite hypocritical as I used to do it myself. However they were a pain in the ass to raid from a citizen's perspectives because people would have their friends standing right outside so that you literally were unable to raid the shop. The only option was to gunpoint them and force them inside, but like I said the place was generally crowded with their friends so the only other option was to use bombs which were an invitation for cops to come along.
I'm pretty sure people still grow in shops, obviously without the defenses, but most of them probably don't grow there anymore due to the inability to have a proper defenses to protect themselves. I don't really see the problem with the usual 3 stack of concrete barriers in a shop as it's a normal type of defense. But the reason the rule was mainly added was because people would try to squeeze in a defense into a small shop generally causing huge movement restrictions when inside, for example this
or this
Now bare in mind these are mainly bazaar shop defenses, and on paint they look like there's far more movement space but if you build it in-game, the space to move in is very minor.
I feel like the rule is fine, people can still grow in the shops if they really want to. I don't mind if there's a normal stack of barricades, but if there's so many props in there that you can barely move, that's a problem and the rule was mainly added to stop those types of defenses from occurring as raiding them was a pain in the ass.