The people sitting behind home plate (visible when using a pitching camera) are causing (at least one of) the heating issues. You can hear the PS5 fans spinning up to max whenever these people are on screen.
This does not occur when using a pitching camera in practice mode (no people in stands) and it doesn't occur if you select a catcher/hitting camera for both hitting and pitching. It occurs less in stadiums where the people are less visible (e.g. a higher wall behind home plate)
To reproduce the issue, simply play a game using a pitching camera that allows the people behind home plate to be visible, and listen to the PS5 fans. They spin up like the system is gonna launch into orbit. Something about these people and/or their animations is unoptimized, so hopefully this gets fixed