Yeah he’s basically saying he used PKHeX to fix the dead battery, after dumping the save with GBA backup tools right? In all honestly I’m not sure if that’s accurate way to deal with dead battery.
It may be possible that when your RTC is resetted, the clock will still run, but only while you’re playing the game, but I cannot be certain, as I do not have a GBA and dead battery cart with me now to confirm.
Also, I'm not entirely certain, but I think part of the steps from the guy above mentions running the save file on a GBA flashcart the rest of the way? In that case, it won't work if you send it back to a GBA cart...
If you decide to proceed, it’ll be at your own risk