[vezuchyy]

They have their checklists and everything, it's not an unusual case when the plane goes to a runway and stops for a few seconds. Again, as an ATC, if you need a passenger plane to get out as fast as possible - be clear about it or don't clear them to the runway. It was also a Fedex pilot who figured what's about to happen by themselves.

[cameldrv]

Yes. The controller should have said "no delay" along with the takeoff clearance, but also given the extremely poor visibility (they couldn't even see 1/4 of the way down the runway), it shouldn't be surprising when a plane takes a few seconds longer on the runway to get situated and double check a few things.