It will be very difficult to recommend Bazzite to friends when I tell them that they have to use Heroic or Lutrix to run their games.
Gamers want to use Steam. And if they can’t do it easily on Bazzite they won’t use Bazzite.
It is just that simple.
Do whatever you need to have good support for Steam on Bazzite or you can just cancel the project.
Steam is already installed as a system package. It is removed from the default app store so that someone doesn’t install it again as a flatpak when it is already on the system which can cause problems and confusion.
Steam is there by default.
well silly me. I totally misunderstood then. Thanks for the clarification.
I think there is a valid point here being, that an app appearing in the app store as “installed” would be expected behaviour. Unsure whether thats solvable though…
Bazaar only handles flatpaks so it doesnt have knowledge of stuff that is on the actual image (like steam on bazzite)
Well, you might say Bazaar does know, since pre-installed apps are being hidden in Bazaar (by configuration).
(At least that’s my understanding.)
You are forgiven 
This is a footgun removal, Steam flatpak is not the Steam RPM, and is severely limited in numerous ways. Some users have installed it and then found their library is missing or worse. All installs of Bazzite come with Steam, it’s unavoidable.
Yeah but this is done by the config as you said. But lets say in general you have application, like Firefox installed “natively” and then you would launch Bazaar (withouth the blocklist) it would still show you to install the firefox flatpak.
Unless the distro has done the blocklist config for it.