Yes, they are totally different activities. Blocking people means that you quit communicating with the users forever. They cannot follow, send DMs, like, share, or comment on your posts. You completely remove them from your life and social media space; it becomes like they have never existed before. People keep following and seeing your posts when you restrict accounts, but there are some limitations. When they post on your content, no one but themselves view the comments. Further, you cannot receive notifications if they send a DM to you. Basically, you limit their activities and interactions with your Instagram profile.