On the main YouTubeTV program guide:
Clicking on the TCM logo (on the left side of the guide) brings up a menu with 3 choices:
LIVE
SERIES
MOVIES
“Live” gives the error messages.
“Series” works, for example the old “Lone Ranger” shows.
“Movies” works, for example “Bonnie and Clyde”.
So it is the “Live” shows that are blocked—they are listed (as you know) but each with an error message (so as to taunt and humiliate). (They call it LIVE but ACTUALLY THOSE are the old movies such as “The Seventh Cross” and “Tea and Sympathy”).