How are maps selected

So question for anyone that knows the answer. I have a theory, but I want others input on how maps are selected.

First off there are a ton of maps in MCC but I feel like I end up playing the same ones all the time which is unfortunate. To back this clam up, in the big team battle playlist that contains halo CE, Halo 2, Halo 2 Anniversary and Halo 4, there are 36 possible maps. This has happened multiple times to me but just today I got the EXACT same map back to back. So lets do a little math. The probability of getting a map is 1/36. The probability of getting the same map twice is (1/36 X 1/36). Which is 1/1298, which is 0.00077 or in percentage 0.077% so either I am a super lucky person and need to play the lottery or something is up. My theory is that 343 only has a select few of those 36 maps loaded on their servers at any point in time. So while it says there are 36 possible maps, those maps are broken into groups, and each group is loaded onto the servers for a specific point in time. So technically you are only able to play lets say 15 (random number I guessed) of those maps during one day. Its just a theory but the face that I never get to play some of the maps listed and it seems like I always have to play relic is annoying.