How is that really any different than screening their phone calls or ignoring them if they come to the door?

There are very few people that are schizoid enough to intentionally ignore a friend who comes to their door.

There are very few people that are schizoid enough to ignore someone saying "hey we're not friends anymore, don't contact me again" and then show up at their house

There are very few people what are schizoid enough to think that telling that to someone's face is remotely the same level as using an online block function. The latter has a much much lower barrier.