I'll be the contrarian and point out what you're missing. Time Effect on Money. If you could receive a 20% rebate now or a 40% rebate in 10 years, which is better? Using a 7% return, the refund reinvested will match a 40% rebate later on...Many people put far too much stock into delaying RRSP contibutions, sometimes its a wash.
If they have multiple children and one becomes a SAHP, the RRSP room can't be used at all (RRSP room can only be used if you're working). This is a level of detail that is hard to guage, only the couple really know their plans. That one requires knowledge of future years, impossible to predict but its safe to say they have the potential of multiple children.
You are also neglecting the CCB rebate by doing an RRSP when pregnant. Its tiny but amounts to a special bonus refund on RRSP when you have a child. RRSP actually generates higher refunds, via the CCB, then otherwise expected.
Its hard to do a complete analysis without knowing a persons details. Hopefully this gives additional food for thought.