From what I've read elsewhere (since the info on Amazon has dropped to non-existent with many titles) only the theatrical versions are included in this set. You wouldn't think it'd be any harder to transfer the director's cut versions from the DVDs, but studios love giving their customers as little as possible.
The "Director's Cuts" were released by the studio, and not endorsed by Richard Donner, himself. There is a separate Lethal Weapon Director's Cut DVD Collection for sale on here if that's what you're looking for.
Yeah, it is BS that WB does not release the uncut versions on blu-ray. I have read other reviews that state this is like the UK version with better video/audio and with 5th disc that does have the additional scenes to view, just not within the movies... They are releasing another 4 disc set on January 7th, 2014, again, appears to not be the uncut versions of the first 3 movies and not even contain 5th disc with the extra scenes. WTF!?
Hard to tell from little info Amazon gives, but they better have the uncut versions this time around. Especially since WB puts this in the description of this set: "Lethal Weapon (1987) With over seven minutes of previously unavailable scenes, the director's cut of Lethal Weapon is a long-overdue present for fans." Oh yeah, long overdue present, you say? Well, where is it then, WB? Why do we have to stop watching the movie to switch to another disc to see the scenes that should have been included all along???