The business scheme is perfectly valid. It’s the same on Instagram as well.
I don’t have an Instagram account and don’t see a reason to create one, but my friends can still link me pictures or videos that I can look at. If I want to engage in any way or read past the couple top comments, I need to create an account.
Showing the user what they came for is a good way to get free advertisement, but requiring them to create an account to actually use the platform is perfectly reasonable.
It shows you the linked post and its content just fine. If you want to engage in the conversation, you should probably just go through the account creation process which takes anywhere from 10 seconds to a minute.