Have to agree with both Flight Detent and Intruder.
With the steel brakes, they get heated for a few seconds between touchdown and when the reverse thrust is fully established.
That's what he's inferring, and he's right, I've seen it a few times. If you leave the autobrakes off you can stomp on the brakes all you like below ~80kts and they just don't get hot.
Not experienced with carbon brakes, but I know from motorsport experience that if you use them, they're best gotten hot to reduce wear. They're relatively insensitive to heat. So I guess in that case you're best to give them that initial heating to get the temps up a bit.