Folks I contacted (emailed) Canon on the EF lens working with IBIS. They wrote:
"The IS Mode option will only show up in the menu when an lens with IS capability is not attached. If you want to reference the manual for that information it is in the caution note on page 238. The easiest way to see the option is to take the lens off, press the Menu button, go to the seventh page under the red camera icon, and when you go into IS (Image Stabilizer) Mode you will have the option shown on page 237. When you enable that setting the in body stabilization will work with any EF, EF-S, or RF lens that you attach to the camera. You do not need to re-enable it for each lens. Once it is on it stays on. "
Then regarding the downgrading of IBIS with EF lens, they wrote:
"From Canon engineer testing the EF lens do not cause the IBIS to be downgraded from 5-axis to 2-axis. In fact the camera's IS along with the lens IS work hand-in-hand when both are engaged."
So in nutshell IBIS works perfectly with EF lens like RF lens. That's so wonderful!!