When attempting to split Tmux windows by using commands, I get the opposite effect of what one should expect:
tmux split-window -v
Produces a horizontal split, while the command
tmux split-window -h
Produces a vertical split.
When attempting to split via the default keybinds it works as intended,
C-b % # Produces a vertical split # or C-b " # Produces a horizontal split
It feels ridiculous to waste time on this, but something is borked, somewhere, somehow. Can post tmux.conf if required.