I know I'm late to the dance, and no one asked, but here's my opinion anyway.
The wiring on the 100 amp circuit won't even fit the HPWC Gen3 connectors(4 AWG maximum). Its not a real big deal though, there are way to adapt the wire down to 4 awg, or I bet there are lugs that fit in a 4 awg space that will accept somewhat larger wire.
I'm also not sure if a 60 amp breaker would fit the 100 amp wire.
The manual itself doesn't say anything about going to a more-than-60A breaker, either. If there's a really awful fault within that HPWC and it starts drawing 90 amps, that hundred amp breaker won't blow until after the HPWC has literally melted off the end of the wires and they cross.
Would I swap the breaker? Probably not. The likelihood of a really awful fault is near zero. The only way I could reasonably expect there to be a failure that shorted the L1/L2 terminals would be physical damage, like a car or lawn tractor crushing the HPWC.