Is Apple Music the same as iTunes?

This can happen to any store unfortunately. If a publisher withdraws, you’d no longer be able to download it. Qobuz has this too. Some publishers are quite scummy with this and upload a slightly different version, which no longer qualifies as the album you’ve purchased. You need to download it asap after buying.

It is, but I found it strange not seeing it in the actual purchaseable music section

Qobuz also does purchaseable music, not just streaming.