Redbeanz,
Unfortunately, at the bottom of Delta's carry on page, they have a vague disclaimer:

AIRLINE PARTNER NOTICE
Our SkyTeamŽ and codeshare partners may have different guidelines and restrictions on certain flights, so be sure to check before you check in


Which is what you did...check with Delta.

But in my limited international trips, I've always been limited/restricted to the operating airlines carry on restriction.
I go round and round with counter checkin about checked baggage which is even more ambiguous.

The one work around that has generally been presented to be when carrying a Pelican attache case with two laptops and power supplies that exceed 15kg...is that when they see the case and weight, they ask if there is a laptop in there, which there is, and it gets a pass. Not sure how many airlines that works with?

Also, anything you can wear on your body doesn't count as carry on. Had to pack 2 sets of professional gear around my body to avoid a $50 charge in Australia earlier this year.