The Drive does not mind importing photos multiple times, even though being advertised differently.
Examples:
- exact same name, created date, but different last modified date => 2 copies.
- modified photo on iPhone => 2 copies (not 1 photo with two different states)
- importing the same photo from multiple sources => multiple copies

This is driving me crazy, as I want to have a single version of a single photo and don't want to waste my time merging etc. The switch to Proton was supposed to be simple.