Heat bed insulation

Insulating the heat bed for the A8 is useless acording to this test:

I made 3 tests:

1. Warm up heatbed to 115, closed enclosure no insulation
2. Warm up heatbed to 115, closed enclosure 6mm kork insulation 3)Manually set the heatbed to 115 when the heatbed was at 90°C warm just to see where the max temperature is (102°C)

For 1 and 2 the heat bed warmed up to 92°C than the SkynetV2 aborted the heating with an error. It is imepressive how identical the warmup curves of 1 and 2 are (desipite some timing issues and the bad data login at first minutes of test 1)

I expected to get faster(up to double the speed) higher temperatures but it didn't have any relevant effect at all.

I assume that the thin insulating layer on the heat bed is already insultion enough and further insulation has no relevant effect.