Most gun makers call all of their newer versions -- which are arguably a hybrid of SA and DA -- "double action". It seems to be more of a "marketing" move than a technical definition -- intended to keep folks from being concerned about an action design that is arguably closer to a SA design than a pure DA design.
I agree with Walt.
The acceptance of the Glock's partly (mostly) preloaded striker in what they call the "Safe Action" as equivalent to a hammer fired double action was a tremendous success of advertising. It opened up untold numbers of military and police sales to agencies that were coming to think of revolvers as obsolete, single action autos like 1911 and P35 as dangerous, "traditional" DA-SA "crunchentickers" as hard to learn to shoot well, and hammer DAO as maybe worse.
Then Glock came along with the Safe Action, which is simple to operate, has a consistent weight of trigger pull but not so short and light as to make executives nervous, and best of all, LOW PRICE.
SA slipped up when they took over importation of the XD. It is a fully cocked striker action and dressing it up with "Ultra Safe Action" prose and a grip safety did not get it accepted by US law enforcement or even IDPA SSP until recently.
Smith & Wesson was paying attention after messing around with the Sigma economy Glockoids and the 990 collaboration with Walther. They flogged the Plastic M&P as "double action" from the start, getting it accepted as such by NIJ in spite of the miniscule movement of the striker by trigger stroke. Selling a bunch of guns, too.
Sig Sauer caught on, too. I look at the P320 as a development of the lackluster P250 DAO hammer gun. If they got it accepted by the FBI, they will do well with it.
H&K has grudgingly gone striker fired, too. I don't know what their market for it is, though.
Likewise Walther, they started out OK with the P99 and are now expanding their lineup. For whom I don't know, either.
But don't mistake the advertising for the machinery.