Apps downloaded from the Play Store appear in the Galaxy Store

[userGGCC6ora9W]

For some reason, most of my apps have been appearing in the Galaxy Store as updates but I downloaded them through the Play Store one app, in particular, is called iMyFone MirrorTo which is an app that allows me to mirror my phone to my laptop but not just this app but other apps like Firefox and headspace have also appeared in the Galaxy Store as updates AND after trying to update them through the Galaxy Store they couldn't be updated so why am I seeing these apps in the Galaxy Store as updates 

[Charkatak]

I have one app that shows up in Galaxy store as well. I believe this can happen when both stores offer the same app.

Galaxy store says it can't auto update the app, but I can manually tap update button.

[Tidbitty · Accepted solution]

All stores can see all installs. If the app itself is also in the store it can say an update is ready.
All app stores can't over write a Play Store install, but the play store install can overwrite 3rd party installs.

[InappropriateAngel]

An app developer can publish their app updates to multiple ecosystems and app stores simultaneously these days. Not all app stores make them available to every user at once. It's often released in waves. So it's somewhat common to see app updates available on one store before another.