The big idea of Alacritty is that it uses the GPU for superfast rendering and updates. But relying on tmux for scrolling seems to be a case of "penny wise and pound foolish". Having to round trip key presses and updates through a separate and possibly remote process (tmux) just to do scrolling, introduces a bunch of latency. "Normal" emulators with built in scrolling don't have this problem. Scrolling is purely local operation.

True.

I use i3 (a tiling WM) though, so tmux is redundant for me unless I work on remote machines.

And I really don't want tmux running on top just for scrolling. It hurts performance quite a bit.