This should be a non-issue if you use Apple’s privacy settings to limit Facebook to only have access to the photos you want to use.
I’d highly recommend never granting any app full access to your photos.
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The solution is just straight up banning apps from the app store which request full photos permissions but only need a picker.
Whatsapp only needs a picker, it's not Google photos. Just make that part of the developer terms and start banning low hanging fruit and the apps will confirm in no time.