The extra hole on the inner rim shell is for a tire pressue monitoring system.
As Tobin said, most wheel manufacturers are really only wheel assemblers.
The inner rim shell you have there was sourced probably from over seas and is drilled to accept a TPMS. Rim shell manufacturers drill the second hole to accomadate TPMS on all the new car models.
Here at Formula 43 we manufacture our own rim shells and drill only the required number of valve stem holes.
Your 3 piece wheel consists of the inner rim, the outer rim and the center section.
Hope this helps.
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