Yeah, and there are also 1000+ other big brands.
Athom is just a small team, they can’t build everything themselves.
As it was made by a consumer like yourself they (the main developer) can make the choice to remove it from the appstore for whatever (good) reason they might have themselves and athom needs to comply with that.
Or there are multiple other reasons an app can be removed from te appstore.
For example, a bad memory leak that makes your homey unbearably slow and it is just not maintained by that (community) developer so it is best to remove it as that is useally the easiest way (and best for the end user) if no one has the time to dig through someone else’s code to try and fix it (that can take a lot of time)
If you really want to know why it was removed you will have to ask athom via their support line (firstname.lastname@example.org) as they are not actively following this community forum.