Not so much retconned as generally disregarded as stories came along that made it useful to postulate earlier interactions. And yes, Khitomer and Narendra count. Interpreting it as official contact is a good after-the-fact rationalization, but what "The Neutral Zone" specifically said is that there had been "no direct contact" since the Tomed Incident, that "For fifty years there's barely a whisper out of them," and that "Everything we know about them is based on rumour or conjecture." Certainly the Intrepid responding to a Romulan attack on Khitomer and the Enterprise-C being destroyed while defending Narendra III from Romulans would seem to suggest more than a "whisper" and more than rumor and conjecture.
Of course, the Romulan attack on Khitomer was established in "Heart of Glory," before "The Neutral Zone." And "Angel One" had the Enterprise responding to a major Romulan incursion offscreen, months before "The Neutral Zone." So TNZ itself was contradicting/"retconning" earlier episodes when it claimed that there'd been "barely a whisper" from them for 50 years. Not to mention that "Heart of Glory" also ignored the Romulan incursion in "Angel One," because Picard said there that "Romulan" was "a name we haven't heard for a while," even though "Angel One" was only five episodes earlier.
So really, the first season is a mess when it comes to information about the Romulans, due to the rapid turnover in the writing staff and the onset of the writers' strike toward the end of the season ("The Neutral Zone" was shot from a first-draft script and didn't go through a revision/error-correction process). The Romulans were mentioned in three first-season episodes and they all contradicted each other when it came to how long it had been since they'd been heard from. No matter what later writers did, they would've been contradicting something from season one.