VNAV/Thrust rating change question

I was in a VNAV climb at CLB-1 thrust rating. I decided to increase the rate of climb by going to full rated climb thrust. I chose full CLB thrust through the FMC, and although it was not obvious that the selection had been made in the CDU, the EICAS showed CLB and the N1 Limit increased to the full climb rating. However, the actual power setting remained the same, as did my climb rate.I switched to LVL CHG mode, and the power setting went up to the new full rated CLB N1 limit. I switched back to VNAV, and the power setting remained at the CLB N1 Limit.Shouldn't VNAV have used the new rating in the first place?Thanks,Don S.