From a quick glance it looks like they are setting up for people to write apps for this specific OS. Surprised, thought they would try and be android app compatible.

No I think they cut off compatibility after a while. I'm not familiar with Harmony so don't know if there is a translation layer.

It’s a fully custom micro kernel design, at least for HarmonOS Next, and from what I heard probably closer to QNX than Linux.

So it would be practically impossible to guarantee all android apps to be compatible, without running them in VM at least.

as per wiki, it seems still alpha and is not shipped with devices?

The Mate 70 is shipping with it… as indicated in the article?

Obviously wiki pages are not 100% always up to date or even correct, which you should know considering you’ve been on the internet for at least seven years…