This approach seems better to me. For one thing, I'd already be screwed if someone malicious got into my Google account, probably worse than if they got into my password manager. And additionally, this means they're not creating an absolute jackpot of data to breach in a centralized place. No one's gonna hack Enpass of all their passwords because that would require hacking all of Google Drive, Dropbox, iCloud, etc. and looking for the files manually.