EWR-TPE is only 300 miles shorter than EWR-HKG
It may have something to do with the routing,
EWR-HKG almost always takes the polar routing on the way to HKG and
the return is usually TPAC.

I also think CO weight restricts the cargo on certain days , while BR might stop to pick up cargo in ANC.
Im sure mr rkkwan might have some more info on this.