While on XSX the custom event labs all run smoothly (and ever did) - I can confirm that the main menu reaction time degraded significantly since the neon update on XSX as well.
When I read this post it does not feel such bad as described on XONE but it is annoying to always have to wait a second now until the next button press is accepted after opening the main menu.
XONE may be older but I am always hearing Microsoft touting how fast a console XSX is.
I am sure this can be done much better on both.