If you choose to limit the photos an app has access to, you have to do it by selecting each photo individually. iOS photos have albums but you can't say "only this album". It tricks you into thinking you can but if you select an album it then says "have fun clicking all the photos in this. have fun editing the setting any time you update that album
I used to think the most annoying album-based ommision on iOS was a lack of album shuffle but that makes sense—apple hates having music and wants use to use their streaming service. This is a newish privacy setting they're clearly proud of and yet they have made the workflow useless enough that I just give everything photo access
