Seraphim additive

I noticed in the simulation data for seraphim haste is shown as multiplicative and other stats are shown as additive. In game haste is definitely additive when you cast sera. Am I missing something? Thanks!

All haste buffs multiply with each other – the only ones that don’t are haste buffs that give rating. All “rating” buffs stack together, then multiply with all other haste buffs.

For example, on the character sheet my paladin has 13% haste. When I cast seraphim, that goes up to 22%. If it was additive, it would have been 21% (even if you account for rounding).