YE had them attack a Klingon outpost. Nothing with SF, so from SF's perspective, they were not interacting with them.
The point is that "The Neutral Zone" said they weren't interacting with
anybody, that they'd turned inward politically. It's not about the Federation's knowledge or awareness, it's about the Romulans' own.
"Matters more urgent caused our absence. Now, witness the result. Outposts destroyed, expansion of the Federation everywhere. Yes, we have indeed been negligent, Captain. But no more."
That pretty strongly implies that they were absent "everywhere," unaware of the overall picture of what was going on outside their borders, or at least too preoccupied with internal affairs (or whatever the "matters more urgent" were) to devote any effort to responding to external affairs. That "expansion of the Federation" included the alliance with the Klingons, after all; indeed, "Heart of Glory" implied strongly that the Klingon Empire had
joined the Federation, and that wasn't clarified not to be the case until "A Matter of Honor" in season 2, after "The Neutral Zone."
Of course, "Glory" does establish the Romulan attack on Khitomer during that time frame, so "Zone" contradicts that earlier reference as well as being contradicted by later episodes like "Yesterday's." (Plus there's the "Angel One" business, but I try not to think about that episode much.) That's the problem with it being filmed from an unrevised first draft due to the '88 writers' strike. Well, one of many problems.
The warbird could be much smaller, keeping the D'deridex reveal intact.
My issue with the
D'Deridex class's size is that it should be impractical for a ship that big to cloak. Cloaking devices are power hogs, and the waste energies from that power use make it harder to cloak a ship, so you quickly reach a point of diminishing returns. That's why the
Defiant had to be such a stripped-down, minimalist battleship in order to cloak effectively; and I believe it's why Starfleet doesn't use cloaks as a rule, because they're just not practical for big, luxurious, multifunction ships like most Starfleet vessels. The hugeness of the D'D Warbirds is hard to reconcile with that idea.