It is. 60mm compressor and turbine. The RHF6 could do 18m3/min (about 48 lb/min, I can't find figures for the earlier RHB6) But the RHB6 is a less efficient turbo. This means more drive pressure to produce the same boost and ultimately lower power and lower fuel economy.
Bigger is not often better in the turbo world. First it's gotta be the right size, secondly it's got to have decent efficiency.

