It isn’t all a one way street, though. We undoubtedly learned something about their defenses by firing the new missiles at them. Sometimes that is just as valuable as the “surprise” obtained by never using them.
It's never a one way street, any Military worth it's salt is always gathering technological intelligence along with all the other.
Both sides try to get the other to spin up their best stuff so they can suck it all up and spit out the best ECM they can build, then do it again.