Does it change the stats of default spells?
In my opinion if not, it's not a magic overhaul.
Does Sorcery's toll change the stats of default spells?
It adds a functionality to them. So does spellcasting chance and a few more mods. Maybe they could be called "Magic Mechanic Enhancer"? Yet it doesn't change their stats, which is the very essence why all magic overhauls were started.
The reason why players choose (or not choose) magic overhauls is because they're dissatisfied with the stats spells have. Some want them simply to be more powerful (-> MM's fans). Others want more reasonable durations (SM and LAME), or want to have some exploits fixed, some specific features... whatever.
Keypoint, in my definition at least, is the changing of default spells. Everything else they do are extras. Of course LAME and SM have grown to include a lot of extras, which is why they can be used together - but only because the idea behind their balancing is sufficiently similar (because there they override each other). Try combining LAME and one of the MMs to see what doesn't work
- again the same overrides, but heavy mod interaction additionally ("Should I summon an Imp, or a Clannfear at level 1? Hmmm...").
On the other hand the magic mechanic enhancers can be used with all magic overhauls (my definition used here) without creating override conflicts.