Mille Fluer is technically a color pattern. Though the Mille Fluer D'Uccle bantam is most commonly referred to as simply that, yes. However D'Uccle bantams come in many different color varieties including Porcelain.
There are folks here on the forum working on Mille Fluer Orpingtons right now, and I've seen Mille Fluer Seramas on the Serama thread.
Most likely though it is the D'Uccle bantam that your local feed store is referring to.
Mille Fleur is a colour pattern.
There several breeds with a Mille variety. D'Uccles, Booteds, OEGB, Cochin, Leghorn & Serama to name a few. I suspect the feed store is selling either D'Uccles, Booteds or OEGBs. Many feed stores get their birds from Ideal & they have all 3.