I agree with you... you should have been moved up into the Stretch section, especially if you had your Summit card, or at the very least, your boarding pass with Summit printed on it.

Boarding priority?
 

Is there a standard system-wide boarding priority for Stretch Seating? I flew SFO-DEN-GRB and return over the weekend. I was late arriving to the gate SFO-DEN so I missed any priority boarding. The DEN-GRB did not have preboarding for any passengers other than priority and those needing more time, as far as I could tell.

On the return, rows 1 and 2 were included in the preboarding at GRB (Republic E190 with 1 x 2 seating in Stretch / Signature) and all Stretch Seating was preboarded for DEN-SFO.

If priority boarding will be a standard benefit of Stretch Seating, it should be noted in the amenities. I definitely would be more likely to upgrade if this is a benefit.

I flew MKE-BOS (Frontier Airbus) last Friday and there was priority boarding for Stretch Seating passengers.

I think they are supposed to board rows 1-4 after Summit/Ascent members, but not all agents at all locations do it.

I suspect there will be some adjustment time for the agents to get used to the new policies.

Give it a few months to become uniform.