Lazy loading is definitely used for exactly this. I’ve done similar stuff in react native. You load “just what you need” which is a couple of thumbnails more than can be seen.

They don't need to cancel each other out.

Lazy loading usually means to load the image at a lesser quality to have something to show the user very fast, so yes technically this can be called opposite of pre loading if used solo.

Pre loading in this instance usually means loading before the user sees the image.

These 2 things can be used together, an example could be to lazy load images at a low quality that are further down the feed before you scroll to them, and load the full image as you get closer to it/have it show on the screen.

But I'm sure the devs knows about thease tricks already

It should barely put any strain at all in all honesty. It’s not preloading all thumbnails, but perhaps the next 10-15 or similar.

Most of the time these would be loaded anyway. It’s only the time when you’re finished scrolling it’ll be 10-15 thumbnails that are loaded and not seen.