That "sharing of technology" might have consisted solely of Romulans capturing some Klingon ships, though...
Invisibility seems commonplace enough in ENT, but it also ends up being a common trick in TOS, the TOS movies and TNG. Yet this does not stop our heroes in "Devil's Due" from jumping to the conclusion that an invisible foe must be operating a Romulan cloaking device specifically! And it's the Romulans who get the Feds to sign a non-cloaking treaty. It appears that there's something special about Romulan invisibility as compared to others... Perhaps justifying the odd twist in "Balance of Terror" where invisibility comes as a nasty surprise to our heroes, even though Archer's old adventures should have prepared them well for such things already.
Another case where invisibility seems to come in different flavors is ST3:TSfS where our heroes immediately realize their invisible opponent must be the Klingons (rather than, say, Romulans) flying a Bird of Prey (rather than, say, a Warbird). Were the Klingon battle cruisers of the era incapable of cloaking, perhaps (despite their Romulan exact counterparts being quite capable)? Or was the telltale optical distortion a sign of the poor cloaks typical of small BoPs, whereas the big cruisers were invariably protected by higher-quality, non-distorting devices? This might take us back to the "D-12 with defective plasma coils" thing from ST:GEN.