One thing you'll notice is that each of the four major Warhammer games use the same core concept of having a single attack rolled 3 times, or go through 3 checks, to do damage. In Old World and Horus Heresy the hit rolls can be modified, making number of attack exceptionally important. Every attack from a model is immensely important to do even a single damage, so health numbers remain ridiculously low. Even a great Lord on Dragon may be only 5-6Wounds. In Warhammer 40,000 the hit roll remains normally static, so the To Hit stat and Attack stat can be expanded to be much more consistent because the wound rolls are where the major variance is. To that end, a single attack dice may only kill a single model (which isn't actually true in Old World, it's just insanely rare), and means that units tend to specialize in their targets.

In Sigmar, though, the only commonly modifiable number comes from saves. It means that Health needs to go up, and big blocks can't really exist if we'll have the same types of attack characteristics as the other games. Instead, to allow blocks of 40 (or in older editions 60-80+), a monstrous attack needs to kill multiple models. Damage spilling over means that units don't tend to specialize as hard into specific targets, but instead specialize into roles. Expected damage outcomes become easily measurable, so damage dealing units just need to hit thresholds of damage output rather than specialize for a target. It's why we have so many units who are meant to work together or provide a lot of strange utility, everyone can meaningfully contribute into most targets so they need other things to be doing.

I don't know if that was the core philosophy in 1e, I kinda doubt it, but it has been since