Common test HE indicators.

Jambijon: The indicator hasn't changed. All it does is takes your shells penetration value and compare it to the armor your mouse is on. The change you're experiencing is just how the HE in this test is calculating damage. Of course you could be looking at a "green" area but your shell may not go exactly where you look because of the dispersion/RNG. We have tons of information that will give you a better idea what's being tested if you haven't read up on it:
CT: https://worldoftanks.com/en/news/updates/update-1-13-ct1/
SPG/HE Test: https://worldoftanks.com/en/news/updates/sandbox-2021-spg-rebalance-results/Pen Indicator wiki: https://wiki.wargaming.net/en/Battle_Mechanics#Penetration_Indicator