I wouldn't. I'd just hold firm.
Still not sure why you say his body clock isn't shifting
. It is. It wasn't 5am anymore. The night was short because he robbed his sleep with a late nap. That is just what happens.
Plus he may never wake beyond early-ish because he is programmed for that time of day.
Doesn't he start school in a week?? I wouldn't go pushing super hard now for that reason alone. If anything you may be pulling back to 7pm bedtimes then anyway as he may need more sleep.