..i mean, I get it, I've written some very scuffed JS in my time because using .filter() right before displaying my data felt easier than getting the right data to begin with. Especially if the backend is in a different git repo and uses some whacky ORM library I'm not familiar with, while the Product Owner n e e d s everything deployed today.

But you can't tell me that applying filter/sort to 8MB of data in the frontend is anything but mega scuffed. Imagine you need to debug that and don't even have an intermediate step to see whether the wrong data is arriving or whether filter/sort logic is wrong for a specific case, or whether its just the rendering. You'd always need a person understanding all three just to debug that one part.
Not to even mention how that would run on low-power devices with bad internet connection. Or what that does to your SEO.