I can't really agree with that. Bringing any plant in from outdoors is definitely a big no-no but growing companion plants with your pot plants can be a big help. Like the RH thing or attracting bugs that wander in to them first then getting them out with the bugs. A lot of plants repel bugs too like garlic and chrysanthemums. Plenty more but I'm not up on all of them.
I grok the using up valuable space thing tho. Wife has two lemon trees in my veg space I want to get rid of. They already survived an "accidental" drying out

so it's time they took up space in the shop window or go outside never to see the inside of my grow space again.