Low speed light aircraft do not use a gate height during low level looping manoeuvres because it is not appropriate with the high pitch rate at the apex and the small radius.
I have some limited light aircraft display experience and I have always used a gate height for what I hope would be obvious reasons. I don’t fly a high performance type such as an Extra so the margins available to me are less, although undeniably greater than in a FJ.
While I haven’t flown FJ, I’m aware that in that case the gate height is also often connected to gate speed - something which does not apply to light aircraft aerobatics. That said, I don’t believe that to say a gate height is not used in low level light aircraft aerobatics is accurate.