There may just be coincidences with a lot of people having similar gear. I often see the same stuff because people aim to get the better gear and obviously level 3 gear will be the most benefit to you. The places with higher loot spawns, and better gear tend to have a high percentage of players dropping at so it's not unlikely you'll see a lot of players with that better gear.
As far as I known in my time playing, and from reading forums and threads about loot spawning, there doesn't seem to be any particular weight applied to certain things spawning in different matches.
Common loadouts are ARs with a shotgun or SMG, in my experience, which is why they're so commonly seen. The more powerful guns have less frequency so that also contributes to seeing more SMGs around the place.
Some early threads like these all mention how it's weighted towards certain zones having better loot, and the farther away you are from them, the more RNG is factoring in. In my experience the more isolated places tend to have some things in them, and a variety of gear, but there is the chance nothing/little amounts of things are there.
If you check out various loot spawn guides like this or this, they'll tell you that you're guaranteed better things at places like the Military Base, the School, or the Power Plant to name a few.
Here is an image which shows the general distribution, and as you can see, some places are much more weighted in the amount/quality of loot spawned. ![enter image description here](https://i.imgur.com/jcvXezO.jpg)
Best Answer
Mid last year a YouTuber gathered community feedback as well as tested on his own to try and figure out how Air-Drops work. In his testing he found that double crate drops would happen infrequently, but in testing never saw more than two drops from the same plane. Though the testing was done before the 1.0 launch (and crate contents have changed since testing), it is unlikely that the number of crates spawned has changed.
Source:
PS: Anecdotally I have never witnessed nor heard of another player witnessing more than 2 crates from the same plane, so it seems impossible or at the very least extremely unlikely bordering on impossible.