Confusion about the Lengthened Partials/ lenghtened position studies

I’m quite critical about the topic of lengthened partials and the lengthened position, but also curious since it’s often not well explained . When these topics are discussed in relation to studies, are they referring to exercises with a resistance profile in the lengthened position, or is it just about working in that part of the range of motion (ROM) regardless of the resistance profile? Also, when they talk about full ROM in studies, which exercises are actually being tested? For example, full ROM in a spider curl versus dumbbell flyes are two completely different things in how they feel.

When these influencers talk about the stretch are they talking about lenghtened bias exercises or just about not skipping the bottom part even in a mid to shortened bias exercise?

There’s a lot of confusion around this topic, and I’d like to understand what the studies are about .