I guess you could be right about Jenny changing in a decade, numbers adding up etc, but what about her daughter? We have no idea who she is yet other than a name Tiffany gives us, she's more than likely about 10 years old in 2009 (let me know if I'm wrong), which would mean Jenny got pregnant in 1999, people have a hard time believing she'd move on from the MC in such a short amount of time. Which leads to people theorizing that Jenny's kid is actually the MC's.Even though I agree with you in principle there is a gap of 10 years from that scene until the power plant incident and many events may have happen to justify Jenny going to the past 20 years to 1989 and then it is many years living a new identity (30 more and on those years some are overlapping 2 versions of her) until 2019 to enforce her resolve about the decision. So isn't that unplausible that it may happen, of course on the basis that this theory is true.
I wouldn't say it is hypocritical, life change us, events change us, a son/daughter change us and we grow and start seeing things differently with a different perspective than when "we" are 21 years old. You simply base your opinion on what she is in that moment in 1999 and it is normal that we do, but there is so many things to explain in the story.
I love a good mystery, and this one mixed with sci-fi time travel. Now the harder part is to explain how Jenny/Ms. Gilmour went from that point A (1999) to point B (2009-»1989) to point C (2019) in a more and less plausible manner and this being a time travel story always raise a bit more my "suspension of disbelieve" state than other genres, so doesn't have to be a perfect explanation because there isn't on paradoxes.
Again, all this with the premise that this theory is correct, that in my personal opinion I'm certain that is correct on a probability of 90%+. It is too many coincidences, even the age of Jackie Gilmour in 2019 "confirms" this theory.
If that turns out to be true, then Darci's mother would be the MC's kid and Darci would be his granddaughter, and because of Patreon rules I highly doubt we'd be allowed for that kind of incest right? Thus I doubt that would be put in the game.