The margin increase is really just from what they define as your third riskiest position if you're in concentration margin mode but it can be very substantial, and it only really matters if it puts your concentration margin near or above initial margin limits as you can trade anything but your three riskiest positions without impacting the concentration margin until you flip back into standard margin mode.
Amusingly not amusingly, I'm now being assessed >200k margin against a position IB marks at 1.00, though in fairness max theoretical loss is ~220k. And ironically I put on the position primarily because it reduced my initial margin requirements substantially at the time, although I did also believe it was good risk/reward.
There was also a separate margin increase on a number of single stocks a few days ago. I'm guessing they broadened out their definition of meme stocks.