In general no, there is no production grouping. MINI has said in many promotional videos that they can build anything in an any order.
Now as I understand Dealers are given slots and it may be possible your dealer had used up all recent allocation slots placing you so far out. I'd give MINI USA a ring and ask whats going on.
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It could also be that a certain Mayfair part is on backorder for the time being and they aren't starting production of the car until that's resolved.