That explains how the takeoff performance got messed up.
But, did they originally request T1 do you think? Numbers looked good with the mistake, save a little time and fuel perhaps. Still, I can't think of many situations where I'd do that in a loaded widebody on a warm evening.
Or, for some reason did the ground controller ask them if they could take T1 for, say, a plane holding with a problem ahead on S? And they checked the EFB, made the #/ mistake and said OK?
I'm hoping the ground control recording will resolve some of these questions.