I am unable to reproduce this bug in Emacs 25 with KDE 5.15, Qt 5.4.2, GTK2 theme set to "QtCurve", GTK3 theme set to "oxygen-gtk".

Using the describe commands (and the M-: evaluation of (frame-height)) causes the frame to briefly expand downwards to accept my input, but it always returns to its original height (35 lines, in this case). 

Best Regards,
Jeff