Since ORD-DTW-SEA would all be flown on DL, then its up to Delta to decide whether it's acceptable. But I think you might be missing the point of the guidance.

Lets say that hypothetically, that on ORD-SEA, DL allows routing through MSP or SLC only. So DL ORD-MSP-SEA, or ORD-SLC-SEA

If we can't find availability on Delta using their allowable routing, we could look at AS for ORD-SEA or the MSP-SEAsegment.

We could also look at getting you to another AS city that:

A) has Super Saver availability
B) is reasonably in the same direction

and connect you there to an AS flight.

Some examples:

DL ORD-MSP-GEG AS GEG-SEA
DL ORD-MSP-PDX AS PDX-SEA
DL ORD-SLC-OAK AS OAK-SEA







Thanks for providing further info on this topic.