turns, applies full power without looking ahead properly (he is trying to save time remember) and then suddenly finds himself taking off alongside another aircraft who entered the runway without telling anyone.
....pretty unlikely with a Pitts, you've obviously never flown one.
If the Pitts pilot had been holding behind the PA28 and then the PA 28 had called lining up and proceeded to turn to the left, then its a reasonable assumption that the PA28 was going to backtrack and that could have been up to 200mtrs which would take some time.
The Pitts could then easily depart from the intersection. Generally he would out accelerate and out climb most other piston aircraft and it would be safer to be ahead of a slower aircraft rather than behind because of the limited forward visibility.
Yes, he should have announced his intentions, but maybe he did and Glush missed it. He does seem to have been wrong on the distance to backtrack and the relative performance of the two aircraft.
I'm no lover of Pitts's but this seems a pragmatic and safe way to maximise the use of a busy airfield.