Interesting! I've just looked (albeit briefly) and, if anything, I think the penalty in Fig 4.13 should be greater than you state, as there is also an 85 ft/min penalty for Anti-Ice ON. Going into the graph with 675 ft/min (to give 150 ft/min) then gives about 24,000 lb.
Not having operated with RIPS a/c or in an icing environment (with this type) I haven't paid much attention to the subject.
Some crews are relying completely on fig 4.9...
Not sure I understand that - surely all crews are using the same planning methods (which hopefully doesn't involve using a printed graph)?