Not really, Bungie can't take all their time for millions, more sense would be that you have a unique id right? The id has some numbers in it that with designed math can form numbers that will assign which weapon kind you'll get dropped more often than others, and which will drop less. I don't believe RNG is 100% random, but I do believe it is random. It is definitely weighted in some way. What I have suggested I'm sure I'm not correct in it, but there are weights to it, for example to raise the chance of getting an exotic weapon you have recently received, has a higher chance than an exotic weapon you didn't receive for a while.