Most of the time, the kids don’t warm up at the proper distances on the side anyway. Usually the kid or a coach incorrectly paces off the distance and the catcher doesn’t compensate for backing off from the point of home plate, so there’s another 3 feet of distance not taken into account.
There will always be an adjustment made after the first 2-3 throws from the game mound. Kids have been making that adjustment successfully for over a hundred years. I wouldn’t sweat the details.
Personally, I often threw the first few high from the mound but quickly got the 3rd or 4th throw in the groove.
Do what works best for you.