@TheWindel Spells do a specific action that is essentially part of the spells 'program/process', Abilities can be freely manipulated at any point, when ever the user wishes.. Example: Spell 'Create Flame' can only create a small flame, it can not move away from your hand/catalyst or it'll disperse, but this can be used to light things on fire if pressed against flammable things or even provide light. 'Manipulate Flame' is an ability that allows one to freely control existing fire to do what every they desire aslong as they have enough concentration.
Basically Spells can't deviate from what their meant to be used without becoming a new spell and requiring other abilities to do so, while Abilities have freedom to do what ever they wish that involves it.
for example since Zahir realized he was one of the people, his 'Control plants (though very weakly) making a piece of grass twitch as he tries to move it.' isn't a spell, that is essentially the ability to Manipulate Plants with enough concentration, that is more than a spell. 'Binding Grass' would be a spell that would cause Grass nearby to grow rapidly wrapping around the target. You wont be able to tell the grass to do anything else without a different spell. or 'Growth' would be a spell to make plants in an area to rapidly grow in general.
Your own spells follow a very basic thing 'Create two small orbs of (element)' this doesn't mean you can fire these small spheres out to hit someone since that wasn't originally part of the spell. you simply made two small orbs of fire or earth. Which still fits a spell, a fairly weak one but still fits a spell.