I guess that is possible, but I think it is just as likely that people just overestimate the requirement. My Pi is practically idling while pushing ~100Mbit bet

I guess that is possible, but I think it is just as likely that people just overestimate the requirement. My Pi is practically idling while pushing ~100Mbit between the builtin Ethernet and an external dongle. Routing really doesn't take as much CPU as people think, even with a few rules for things like bandwidth monitoring on a per IP basis.