The problem you're overlooking is that the $1 million is in future dollars, not current dollars. You have to discount the $1mil at the presumed investment return rate for all of the years between now and when you can collect it. That will give you its current value.

Example: If you're 40 years old today and already eligible to collect $40k/year at age 60, then if you assume a 4% withdrawal rate (probably high given how pensions are managed) you correctly forecast the future value as $1mil 20 years from now. If you then assume 7% total return between now and then, your pension is really worth about $250k today. So if you had $250,000 in hand today you could invest it at 7% and it would be worth $1mil in 20 years, from which you could start paying yourself $40k/yr.

This sort of Net Present Value calculation is very sensitive to the discount and payout rates you use, especially for long time periods. I wouldn't put too much faith in it.

A better way to think of it, IMO, is to subtract the future $40k/yr off of your future (inflated) living expenses in real dollars. Then figure out what size stash you need to support that newly reduced amount of expenses. Otherwise your'e making assumptions both forwards and backwards that might turn out to be wildly wrong, and doing so for no good reason. Subtracting the pension from your expenses reduces the number of unknowns down to just one, your future expenses, and then you can focus on things you can actually control, like your savings rate.

Of course, it does complicate your desire to "pad" your net worth calculation. Let it go.