ip xfrm policy help gives invalid output

On Ubuntu Focal, the `ip x p h` command from iproute2 (5.5.0-1ubuntu1) gives the following output:

    UPSPEC := proto { { tcp | tcp | tcp | tcp } [ sport PORT ] [ dport PORT ] |
                      { icmp | icmp | icmp } [ type NUMBER ] [ code NUMBER ] |
                      gre [ key { DOTTED-QUAD | NUMBER } ] | PROTO }

I don't think the proto is intended to be "{ tcp | tcp | tcp | tcp }" or "{ icmp | icmp | icmp }"

The same command provided by iproute2 in Debian Buster (4.20.0-2+deb10u1), Bullseye (5.10.0-4) and Ubuntu Groovy (5.7.0-1ubuntu1) generates the following output, which looks like intended.

    UPSPEC := proto { { tcp | udp | sctp | dccp } [ sport PORT ] [ dport PORT ] |
                      { icmp | ipv6-icmp | mobility-header } [ type NUMBER ] [ code NUMBER ] |
                      gre [ key { DOTTED-QUAD | NUMBER } ] | PROTO }

It certainly makes more sense that proto may be one of "{ tcp | udp | sctp | dccp }" than "{ tcp | tcp | tcp | tcp }".

Should any relevant fix be ported to the LTS version, Focal, too?