Why are pipes in bash 5.05 so slow?

Question

I'm running a bash script that makes extensively use of piping. In bash version 5.0.17 (running in Ubuntu 20.04.4) the script is really slow. I did some simple test and I found odd results:

$ bash-5.0$ time for i in {1..10000}; do echo > /dev/null | echo > /dev/null  ; done

real    0m21.716s
user    0m25.496s
sys 0m14.913s

Removing the pipe:

bash-5.0$ time for i in {1..10000}; do echo > /dev/null ; echo > /dev/null  ; done

real    0m0.097s
user    0m0.071s
sys 0m0.026s

With other bash version I got different (best) results:

bash-5.1$ time for i in {1..10000}; do echo > /dev/null | echo > /dev/null  ; done

real    0m10.255s
user    0m9.366s
sys 0m7.084s

With bash 4.4:

bash-4.4$ time for i in {1..10000}; do echo > /dev/null | echo >/dev/null ; done

real    0m9.620s
user    0m5.010s
sys 0m7.528s

Any idea why the pipe behaves so badly?