I think it's very tricky to assign this level of real world specific equivalence, because the making you hit/wound/save as a sequence is mostly there to let you roll more dice and interact with more mechanics.
They could replace everything with a formula that results in a single number you need to beat on a single dice fairly easily, and go even more in depth with it, but that's not very interesting.
Having the roll sequence allows for a lot more "oooooooohhhhhhh" moments without up setting the rhythm of the game and means that each player gets more interaction with abilities and leader buffs etc. And it's fun to roll lots of dice.
IMO it would make more sense to say that the combination of stats represents the general resilience and armour of a model, but that assigning each step of the sequence this level of specific equivalence is reading to much into it.