I'm very far from being a young millenial and though I don't program PHP, I used to program computers at a fairly high level.
I'm aware that computers can't generate random numbers, they only appear to. Computer languages have built in functions that will generate pseudo-random numbers given an initial seed and it's child's play to create that seed.
You would know very quickly if the seed was the same each time because you would get exactly the same set of numbers each time you played the game as you said. What you would not get is a skewed set of numbers that produced odd results that people typically complain about.
And you most certainly would not get a system that actually cheats to achieve some kind of desired outcome e.g. allow beginners to win more often. As I said, you can't do that by simply rigging the initial seed. It's actually a fairly complex task because you have to program in what is a "good roll" of the dice. In many games it's not obvious what rolls are good and which are bad because it's so context sensitive. It could be done but it's not simple task and you couldn't do it accidently.