Yeah. Sorry I forgot to mention that. The "timer" on the G5 transmitter is software based in the G5 receiver, so there is no way around that except to use a hacked receiver like xDrip+
The good news is that in the past month I've found that the xDrip+ algorithm seems to more accurately report bg according to finger sticks. The phone software is also far more complete than I think Dexcom will ever be ( IOB, prediction, momentum, bolus calculation, etc).
I understand your child is pretty hip to managing his Bg, maybe he (and you) would consider trying out xDrip+. I'm using a Sony Smart watch 3 as the receiver and it's very convenient. Capture rates in the mid to high 90% range.
Best of luck to you and your child!