The laser is on a mechanism that moves in and out from the center to the rim of the disk. You can see a picture here: https://gametrog.com/playstation-1-one-information-specs-ver...

I don't have a Playstation myself on hand, but from memory, these mounts usually had a certain amount of play in them - if you touched it, you could press it a bit lower, for instance. Whereas the clamp that grabs the disk on toploaders tended to make a very secure connection. So it's probably not bringing the disk closer to the laser, it's bringing the laser closer to the disc.