No brake temperature indicators on the 757-200's I flew as equipped from Boeing.
Also, the 757-200 for Take Off use flaps 5-15 or 20
Flap 1 take off only on 767-200's.
For rejectd takeoffs; in the Boeing normal procedures section is a page with graphs based on weight, brake application speed, pressure altitude and OAT. Using the chart guides one to recommended action following rejected TO.
Generally for heavy (loaded to cross an ocean) ops an abort at more than 80 knots is gonna lead to some brake cooling time at least......and if enough energy has been absorbed by the brakes, fire fighting intervention may be necessary.
Who knows what they saw on the flap indicator panel or what their planned flap setting versus what they had was. I do know that having one Check Airman on the flight deck is cause for concern.... having TWO or sometimes more cause some concerns every now and then to FO's along for the ride.
I was a line type 757-767 Check Airman or LCKA for 15 years.