Why still no dive acceleration difference?

[Crumpp]

Hardly, the electrical priming on the Fw could deal with synchronised fire rather easily. Much better than other systems.

Yes it could compared to a mechanical sychronization but the electrical priming cannot change the limitations of the weapon itself.

As for what you said about 4 blades propeller and cowling/wingroot weapons firing through the prop disc, although very rare, there were some aircraft with this configuration:

Interesting and rare....

I was very surprised to see a German aircraft with a 4 blades propeller

If the performance differences had been noteworthy, I think the Germans would have used a 4 bladed design. As it was, they had good propeller designs and increased chord width which accomplishes the exact same goal of being able to load more power onto the disc.

The Germans also used wood in many of their later designs as it is a much better material for power loading than metal.