Why still no dive acceleration difference?

[Crumpp]

Do you mean these are just to get an idea of general trends?

Yes

It seems that allied believed in wwii that 4 or 5 blade propellers are better than 3-blade when speed is high(>700km/h?).

Power absorbtion is what they were going for....

3000 hp engines where the next step on the horizon.

Large amounts of effort for little gain in a 3000 hp piston engine aircraft.

Jets eclipsed any further piston engined development.