The point he's making is more flow isn't always better. There's a point of diminishing returns, where, as he said, flow is so fast it won't pull heat out efficiently. The Terminator pumps may be on the weak end from the factory (so it'll last years, instead of crapping out after 1 year) so an upgraded pump may be beneficial.
But also say, a 5 gph pump may not flow enough on a larger AWIC but may be too strong for smaller one. What I'm trying to say is, you have to match the flow rate to the system instead of just saying one pump is a catch all, for all systems.