slow thunderbolt 3 transfer speed using thunderbolt bridge and 2 new mac

Hi,

I have 2 apple machines:

A) mac mini 2020

B) macbook pro late 2019

The speed of the hard drives on the mac mini and macbook pro is very fast, after doing tests I get:

(I'm using blackmagic speed test software)

HD speed on machine A and B over 1200 Mbyte / s write speed and over 2500 Mbyte / s read speed.

I connected the 2 computers via thunderbolt 3 (intel certified cable).

I set the priority order under network preferences: I put on top " thunderbolt bridge'

I did several tests transferring files between machines A to B and B to A.

My average speed is around 200 Mbyte /s max speed is around 350 Mbyte a second.

Why ?

Why is so slow ?

The thunderbolt 3 connection cannot be the bottleneck here.

(It can go up to 40 Gbit/s)

40Gbit/sec = 5000Mbyte/s !

I should be able to go close to the speed of my HD right?

(ok may a bit slower) but not 3-4 times Slower ?

I'm expecting to go at least at 1000Mbyte /s (8Gbit/s)

Please can someone from apple help me out?

I did call apple support 3 times!

I didn't get a clear answer.

No one could explain why I'm getting this slow speed trasfer.

Thanks

Dani