Thank you again, I've great news this time as well. After updating the newton_atspi_compat package the flat review with newton is working fine. With nautilus it started to work immediatelly when I've restarted orca with the updated newton_atspi_compat package in place. With fractal it started to work after restarting fractal.
Also I must say I have found my-self reporting a strange thing yesterday. I have mentioned I have tried gedit as a part of this testing however now I have realized gedit is a GTK3 app not GTK4.
When looking at gedit main window I can use orca's flat review to explore its toolbar including moving the mouse pointer and synthesizing mouse clicks. When doing the same thing with GTK4 apps such as nautilus or fractal the flat review is working great but emulating the mouse is not.
Excuse me for this mistake. I got it wrong.
And just now I have noticed another thing. I wanted to verify the mouse emulation features by running gtk-demo app which is GTK3 app too. I have tried to run gtk-demo from the gnome-terminal. As it has started I have noticed orca briefly reporting GTK demo however I can't focus its window. When holding down the alt key and pressing the tab key to cycle through the open windows, I can hear GTK Demo is part of the window switcher but when releasing both the keys that window is never brought to the foreground. When expanding activities from the gnome top pannel I can't locate GTK demo either. The very same thing has happened to me with an electron based app called losslesscut but originally I have assumed that was a momentarily thing related to electron but now when seeing it for the second time with a different toolkit I am wondering if this might be related to the mutter changes.
I am sorry for mentioning too many things. For some of these I am really unsure so if it's not relevant please ignore those parts.