Nope, they've always been that way, no training required. My husband can go to bed at 4am and will still wake up when the sun comes out.
If left to my own devices, I run on about a 28 hour day and will eventually go fully nocturnal. That said, I have trained myself to go to bed at 2 and wake up at 10. But if I try to go to bed at 9pm so I can wake up at 5am, all that will happen is that I toss and turn until 2 am, then wake up at 5. No amount of training will fix that. I averaged 4 hours of sleep per night back when I was in school, simply because I could not go to sleep that early.
So while training is absolutely possible, I think you're underestimating the power of the natural circadian rhythm and how people react to it.
@Jamixthedestroyer My husband and stepmom are that way. Sun's out, and they're up and chipper. Meanwhile, I don't even begin to feel tired until around 2am, and the mornings are just a bright, miserable blur.
@gamarus While I can't speak to 1.19 to 1.20, I did have a server that updated from 1.18 to 1.19 back in the day, and we were able to update it without any issues. You just put the mods in the required folder and delete out the old ones, and it should keep the information.
That said, definitely make a backup before messing with anything, and if it's giving you any trouble, you can always pull the world files down to your computer, update the mods, then reupload it back to the server (I had to do that a couple of times).
Good luck!
Edit: I just realized you were asking about Forge. Full disclosure, we used Paper, so your experience might differ. Sorry about that!