See here:

https://github.com/ipython/ipython/issues/6974

Chet Ramey confirmed the bug is downstream:

As I recall from looking briefly at the ipython/python source code, it has
to do with python not handling the SIGWINCH and expecting readline to do
it even when readline is not active. In readline-6.3, readline only
installs its signal handlers when rl_callback_read_char is called, which
python does only when it receives a character and its select(2) call
returns. The way readline-6.2 and earlier did things, it could `steal'
signals from an application without being active. I think python doesn't
handle SIGWINCH at all, which means that it expects readline's signal
handler to be active all the time, instead of just when python calls back
into readline to have it read a character.

A possible fix would be to have python's readline module install a signal
handler for SIGWINCH and have it set readline's idea of the screen size.