multiple track selection, via Shift or Ctrl+click modifiers, is about and only functional to group-toggling the track buttons, [R], [M] or [S], at once.
changing multiple track's height is not there applicable, as you may confirm that any previous selection is reset when you start dragging a track's bottom edge up or down to change its individual height.
no, you're not doing anything wrong.
multiple track selection, via Shift or Ctrl+click modifiers, is about and only functional to group-toggling the track buttons, [R], [M] or [S], at once.
changing multiple track's height is not there applicable, as you may confirm that any previous selection is reset when you start dragging a track's bottom edge up or down to change its individual height.
cheers