> they made an offhand comment contrasting its abilities with Git's, referencing Git's approach/design wrt how it "stores diffs" between revisions of a file. I was bowled over.

It seems like you have taken offense to the phrase "stores diffs", but I'm not sure why. I understand how commit snapshots and packfiles work, and the way delta compression works in packfiles might lead me to calling it "storing diffs" in a colloquial setting.