Just to make sure, did you also unfollowed that account? Instagram suggested that users should find new accounts to follow if they want to remove the unwanted posts from their feed right away.
I've had Instagram for years. This has not happened before. It's a recent glitch. I have a private account, I only follow acquaintances. Recommended accounts are identified as such and I ignore them. These are in the normal feed, not in the recommended accounts listing. And they are random things I have never shown an interest in on any platform. Makes no sense. This is not a normal Instagram behavior. These accounts have been blocked for weeks or months. They just started posting in my feed recently, still showing as blocked.