Well, at this point I’d guess we’re in the realm of details that won’t be shared.
It may be that decoys weren’t mentioned by the US because they involve new, classified technology. Or the number of decoys was included in the count of total missiles launched but not in the “all missiles hit target” statement.
Given the classified nature of newest technology we should expect some deception in descriptions of the attack, as well as (perhaps) in descriptions of the defense.
The number of airfields where “all missiles were shot down” or with “no significant damage” suggests decoys to me (with, perhaps, small explosive charges to obstruct after-battle analysis). Purely decoy attacks on pseudo-targets seems like a realistic tactic.
Note that according to US descriptions (in your second link, etc.) all three national participants launched some of their missiles from aircraft, including the US-launched JASSM-Extended Range (JASSM-ER), which saw their combat debut here.
(According to FlightGlobal “The B-1B Lancer has a payload of 75,000lb (34,000kg) and can carry 24 cruise missiles,” but “two Boeing B-1B Lancer bombers fired 19 JASSM-ER weapons” which would seem to leave plenty of payload capacity for ADM-160C “MALD-J” decoys.)