Cold Damage Over Time Question

So on CDoT skils like Arctic Breath there is a line saying 'Modifiers to Spell Damage apply to this skill's damage over time'.
Doest that mean that ONLY spell damage modifies CDoT and for example % increased cold damage or % more elemental damage don't?

those work just fine

the reason why there is such line in skill description is that under normal circumstances spell damage cannot apply to DoT because these base damage types are mutually exclusive

Ok thanks!