He has already told us that his machine had better performance than a Pitts. With a long hard runway no way did he need the extra 20m to comply with the regs. He probably had more than 5 times what he needed.
If it was an F4, it uses a lot of runway before achieving a 48,000 feet rate of climb, which I believe might just beat a Pitt's.
And that answer is about as sensible as yours, as you have no more idea than me of the performance calculations for that aircraft, which might even be simulating an IFR departure in a multi for training purposes.
Let's face it, the whole thing is about communications.
"G-ABCD making short backtrack before line up and departure"
"G-EFGH entering behind backtracking aircraft for immediate departure"
Would have probably solved probably the whole misunderstanding.
Possibly not, as G-ABCD was a AVRO 616 AVIAN MK4M, withdrawn from use in 1938 and G-EFGH is a Robinson R22
Sorry couldn't resist!