Do you expect that this skew would meaningfully alter the conclusion? That there are many men on their deathbed who wish they had more time for brunch in their life vs the hard work of parenting?
The spectrum goes from, I've talked to quite a few people who only talk about negatives of having kids as long as they are talking about anything specific (health, hobbies, friends, work, even their spouse), but as soon as they start talking in abstract they reiterate how having kids / their kid is great. Usually 5 minutes after an endless stream of complaining. It's either Stokholm syndrome or social desirability bias...
To, I know / knew lots of people who are either terrible to their children or whose parents were reportedly terrible to them, anywhere from emotional distance and clearly not wanting them around, to outright physical abuse or extremely controlling behavior, or basically abandoning them to their own devices. I fully expect people like that to regret having kids, but I've never heard or read anyone admit it.
I think having kids is a boring chore that (pretty much by definition) nearly anyone can learn to do. Sure, it might be necessary, but that combination makes it about as special, fulfilling and exciting as farming rice. Most would rather have brunch, so perhaps we should pay people to do it. Except that with kids, you cannot admit that you'd rather have done something else...
Of course comparing to "brunch" is done in the same snide spirit, but even disregarding pastimes that are actually fulfilling, I'd also much rather have more brunch :)
To answer your literal question -imagine someone dying from lung cancer in their 40s. If they regret smoking and wish they never started, should that have, in retrospect, dictate their life decisions? Or do the "thousands of days" they happily smoked matter more?
I find that most success in life comes from this ability to mentally associate with your ultimate self and do things today that will make that person most satisfied. Which happens to also be way more satisfying in the moment.