The problem is the term 'leave in' is being used to mean more than one thing and that is confusing for many.

In Curly Girl terms 'leave in' is shortform for leave in conditioner, by all means modify CG to suit your needs and use an oil or butter or detangler instead but then say so - oils or butters are sealers.

If we start using the term 'leave in' to mean anything that is not washed out then that is every true leave in conditioner, moisturiser, detangler, sealer, curl cream, gel or mousse. The term is then so broad as to be uninformative.
2a-2c, medium texture, porous/ colour treated. Three years CG. Past bra strap length heading for waist.

CO-wash: Inecto coconut/ Elvive Volume Collagen
Treatments: Komaza Care Matani, coconut/ sweet almond/ fractionated coconut oils, Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss Ultimate Volume, various Elvive
Styler: Umberto Giannini jelly, Au Naturale styling gelee
Flour sack towel, pixie diffuse or air dry.
Experimenting with: benign neglect