Steam's dialogs (e.g the startup dialog, login dialog, settings dialog, download dialog) do not have _NET_WM_WINDOW_TYPE set to _NET_WM_WINDOW_TYPE_DIALOG, as dialogs should have (you can easily check with xprop, and compare to dialogs opened by almost any other application). See also here: https://specifications.freedesktop.org/wm-spec/latest/ar01s05.html under _NET_WM_WINDOW_TYPE.
As a result, window managers which apply rules to dialog windows specifically will not correctly handle the steam dialogs; for example, a tiling window manager might not want to tile dialog windows but set them to floating instead, especially when they are additionally not resizable like the steam ones.
Steam's dialogs (e.g the startup dialog, login dialog, settings dialog, download dialog) do not have _NET_WM_WINDOW_TYPE set to _NET_WM_WINDOW_TYPE_DIALOG, as dialogs should have (you can easily check with xprop, and compare to dialogs opened by almost any other application). See also here: https://specifications.freedesktop.org/wm-spec/latest/ar01s05.html under _NET_WM_WINDOW_TYPE.
As a result, window managers which apply rules to dialog windows specifically will not correctly handle the steam dialogs; for example, a tiling window manager might not want to tile dialog windows but set them to floating instead, especially when they are additionally not resizable like the steam ones.