This is ridiculous. Anyone could have looked at the test results for Javelin and seen that it would be successful against modern armor. Same with the Ukrainian Skif and Stugna ATGMs, the UK's Brimstone and the NLAW. All of these had been extensively tested by multiple parties and found highly effective.

And the threat posed by ATGMs to improperly deployed tanks has been well understood since the 73 War where Israel first faced the Sagger ATGM.

Also, ATGMs didn't play a big role in either Iraq or Afghanistan, especially against armored vehicles. In Afghanistan the Javelin was used primarily as a bunker buster or knocking on cave doors. In Iraq, both TOW and Javelin were used for breaking up fortifications. Hellfire was used in the abortive Apache raid that showed how useless helicopter gunships were in a contested environment with lots of AAA.

This idea that there's a secret arsenal with staff and personal briefed on a need to know basis is just conspiracy theory. Sure, there are weapons in development that are secret, and specific capabilities are secret, but there's very few silver bullets hiding out in Tonopah or White Sands.