Recently, I had my own experience with this issue.
In my case, an app that I had installed through the Play Store some time ago informed me upon opening it that I would no longer be able to use the app until I had updated it, supposedly since a recent major upgrade introduced breaking changes.
This was rather curious to me, since I update apps regularly, and I hadn't seen any updates for this particular app in a while.
When I went to perform the update however, I was greeted with the aforementioned error on the Play Store: "Your device isn't compatible with this version", and so was stuck with the non-functioning app.
During my attempts at finding a workaround, I was able to use the Aurora Store to download the most recent version of the app, and it installed from there without issue.
Curiously, considering that the suspected cause for these "soft delistings" on the Play Store is the Play Integrity API, I received no notification from GrapheneOS that a check through the Play Integrity API had been attempted by the app itself.
If the cause for these "soft delistings" is indeed the Play Integrity API, then it seems that some lazy developers are only choosing to use it to delist the app from the Play Store on certain devices, but without directly integrating the API into their app.
Perhaps the most frustrating thing about this however is that I received absolutely zero notice by either Google or the developer about the fact that the developer had made this change and Google was withholding updates to an already installed app, due to which, as a consequence, the app may have remained on an old version with potential security issues for many months before I was able to spot the issue.