The shell does not resize Emacs child frames when requested.
When emacs creates a child frame with certain dimensions and then changes them gnome-shell does not reflect those changes.
This happens only in gnome-shell (I tested 3.34) and not in IceWM.
Test case: This little script creates a 40x10 child frame and then changes its height to 20. (My first time writing elisp, so any elisp hackers out there, watch out!) What happens is that the frame size stays at 40x10.