I wouldn't want to answer on behalf of the department, but I think it's fairly reasonable to assume that some folks on staff understand how RRSPs work.
Now, the key point to make is that this committee has been repeatedly told that various estimates have not taken into account the downstream taxes paid on withdrawals for RRSPs. That's simply nonsense on stilts. The committee is being misled on that score.
The money flowing into RRSPs is deductible in the first place. If you do a present-value calculation, you have to allow for both. If you don't do that, then you're simply wrong.
So as I said, it's simply nonsensical to not allow for the fact that the income flowing is deductible in the first place when you talk about the taxes paid on downstream income.