Always happy to let people in the shops normally lead them there and wait inside to lead them back just in case anyone gets lost. I haven’t had any issues myself in doing this.
I don't usually host, but when I visit someone I do ask always if I can visit their shops. Usually I ask only when I'm at least acquaintances with the person. When I trade with a stranger I'm always too shy to ask, so sometimes I wait for the host to tell me it's okay to visit their shop
I actually just did a trade and had this happen to me lol. Then they asked me if I know which villager was crafting. It was so strange, I just wanted to do a quick trade but I felt bad and wanted to be nice