This was stated a long time ago by Blizzard, the 10 man and 25 man are on different raid IDs
There's a tow fold reason:
1.) They are already two separate instances (as in, they don't contain the same mobs, each mob has to be programmed differently)
2.) It would take so much programming to make them lock each other, and store extra unused data on the server that it's counter productive to make them lock each other out.
I found the answer, but cannot delete my own topic.
(the answer is yes)
dont know where you found that info but its wrong. on the beta I cleared 10 man one day and 25 man the next day while I was still locked out of 10 man. add to that bliz posters have stated multiple times that 10 and 25 man raids were on separate lockouts.