Kim Dotcom did this and it lead to Riaa saying it obligated the file sharing service to look for all copyrighted materials. This opens pandoras box for Apple.
No, it didn't, at least not legally. There is no federal requirement to scan for copyrighted content (which is an impossible task without $MM in capital and a media library of copyrighted content) - YouTube only does it with Content ID to appease the rights holders and not have them remove all their content from YT outright. The only requirement is to respond to DMCA takedown notices, which they were obligated to do before Kim started scanning for CSAM (which I can't find a story for).