This is the true result of equivalence. I had 160k HP gained from HP affixes and sets that multiply HP and equivalence also makes sure MP is the same value as HP. Essentially to force 100% equality and it goes great with Equality set.
Also for the damage reduction and resource cost. If you have full HP/MP at 100%, it's gonna reduce DMG by 65% and resource cost reduced by 60% . Since it's based on equality and that people need equivalence full to achieve the 65% damage reduction, I can safely assume that if you have missing HP% and MP%, your damage reduction is reduced in that regard.
That's why builds like cronos Fortune Bringer had to use harmony + prayer back when prayer was OP to keep both MP/HP full for full 60% reduction.
In pvp, there are builds that work similarly on that principle where you hit the build but it keeps staying at full HP , although that can also be done by Alchemy Mythic but my bet is that it's equivalence for high DMG reduction for the 'immortal' builds' as well as every other possible damage reduction.