I actually feel the opposite way! In general I'm much more likely to listen to a full length album rather than a single track, so when some singles aren't included on an LP it means I'll end up listening to them less compared to the music on a "proper" album.
Most of their songs do have vocals, I did think this instrumental one was kind of an odd choice for a single. Definitely check out the previous album (Phanerozoic I) if you haven't already! It was one of my favorites of 2018
No, those were part of the original release - this album was a compilation of b-sides and demos to begin with. Looks like it got a vinyl pressing done back in July so maybe that's why it's being posted.