Originally, there were four separate Trial of the Crusader lockouts: ToC10, ToGC10, ToC25, and ToGC25. This allowed us to do the same raid four times per week, as it was originally designed by Blizzard.
Currently, however, if you complete ToC10 and then try to enter ToGC10, you fall directly into Anub'arak's pit with 50 attempts remaining. Why was this changed? I searched through the Warmane changelogs, but I couldn't find any mention of this change.