Never heard about this, source? Toddlers tend to be somewhat exempt from mask mandates because they're toddlers and everyone understands when they don't comply.
We have two children. Both masked for 7 hours a day. Every day. Both schools are VERY STRICT. Everybody is vaxxed and boosted. Doesn't matter.
The TSA mandate itself. Only those under age 2 are exempt from it. This is just for the US obviously, not sure about other places. But in my experience the less you paid for your ticket the more strict the airline is. I typically don't fly budget airlines but did once during the pandemic and that's when a flight attendant shouted at me and my wife when our toddler had taken his mask off and we didn't notice.
I've flown in the past year and was annoyed that adult passengers in front of me weren't wearing their mask (or wearing it with their nose exposed). While the flight attendant told them a few times times to put their mask on correctly, the flight attendants were not going to "turn the plane around and ban [them] permanently".