I know of some people that never use 403, but instead opt for 404 for security reasons. 403 implies that there is something they could have access to, but don’t.

I think in some situations that this can be valid, but it shouldn’t be a crux.

I think he means that by contributing to the likes of threads legitimises the platform. And when you “create content” there, then you’re essentially doing free labour for the venture capitalists, since their asset is only valuable if people use it.