Unless he got that from Rockstar itself, I doubt it is true, and even if he did, I still kinda doubt it. Rockstar is very very strict about Beta content leaking, so much that devs usually hang around this and GTA V's Beta Hunt thread looking for portfolios to delete, and I even doubt Rockstar themselves still have early builds of games. The only way I can see that is if he got that from a Journalist or something.
But then again, i'll judge that when I see it.
It's true, trust me.
Person has given me some builds of games before. He has alot of confidential stuff. (his room is filled with developer kits of all kinds of systems)
GTA beta's arent as rare as you think they are.
There was an EFLC build floating around Assemblergames.com that i almost got my hands on.
I also knew a person who had a SA beta XBOX disc once, never got my hands on that aswell.
Plus ofcourse the more well-known San Andreas XBOX debug build that was ''sold'' on Assembler. It was discussed here in some San Andreas beta topic before...
So yeah, this is 100% real and you'll soon be able to see some kind of GTA IV build for the first time.
But just not extremely early. Still something though.
Also, alpha builds don't necessarily have to come from Rockstar themselves. Rockstar tests their games out on developer kits. They put builds to tests on their developer kits. Sometimes they forget to wipe the HDD before the developer kit is sent back to Microsoft/Sony or China (out of all things, also the place where they get sold out to the public).
Alot of devkits that weren't sent back to MS or Sony are sold on collectors website, alot of times having good stuff on the HDD. This can be one of those cases. Although i heard it was most likely a beta disc that was given to a journalist. Still fascinating though.