Solo standard is not a mode that can be understood. I'm 90% solo queue for standard as well and see the same thing. Even though you would think solo players willing to do implicit teamwork would be the normal for solo standard mode it seems to be used as more of a joke mode for people who don't want to risk their standard rank, so people ignore rotations and go for balls they normally wouldn't. I think as such maybe it emphasizes mechanical skill over intelligent play, at least I feel like my mechanical skill is usually the thing lagging behind, and my solo standard rank is a little harder to get up. There might be an element of low population at play as well, something with the ranking algorithm not filling up to the top ranks properly. I don't know.
But it's definitely a weird playlist.
But it's definitely a weird playlist.