What specifically? That PPPoE is slow? Are people really running PPPoE at gigabit speeds? Are there actual fiber installs using PPPoE? or is this for VPN usage?
It does look like pppoed is using netgraph, so it should be resonably fast. I think it's more of a problem of networking/firewall just being slow on lower end arm boards, and why I switched to a SFF PC for my internet router:
https://flyovercountry.social/@encthenet/110895206283732462