With the exception of the late 20ga skeet guns, for whatever reason, short barrels on the Ithaca SKB 20's were always 25" and the long ones 28", while the 12ga short barrels were always 26".
I can't recall ever having seen a 12ga Ithaca SKB with 26" barrels choked M/F. 28" were typically M/F, short ones IC/M (except the skeet guns, and except some of the 25" 280 20's which were IC/IC). However, there were some exceptions. I owned 2 Ithaca SKB 12ga 150's--a somewhat rare model, PG/beavertail and engraving like a 200 but without automatic ejectors--which had 28" barrels and came from the factory choked IC/M. So I would not say it's impossible that a 26" 12ga 280 might have been factory M/F.
