Note on #2 above that there are other LB/RP projects that don't have a problem here because they chose to be single threaded. This means their performance is not greatly impacted.
HAproxy is incredibly performant because the project chooses to prioritize performance. Also, as an open source project, we should applaud the efforts of the team to provide the best product possible and not just push everything of value into the commercial offering.
Thats pretty rare these days.