Who knows if they are doing lognormal or normal distribution but thinking a market maker can or would want to change their code w/o little notice, ability to test or incentive isn't realistic.
CME gave them plenty of notice (1 week). No coding changes needed. All they need to do is switch their BS, Whaley, or Binomial theoretical models to Bachelier or Normal No Bounds and just mass quote strikes as usual.
These MMs are paid and/or rebated through the market-maker incentive program to make reasonably "tight" two-sided markets in all of the expirations they are assigned to. So basically it's their job to provide liquidity for the exchange, and they are rewarded handsomely for it.