He could be a Mille Fleur Booted Bantam but I'm not aware of any hatcheries that carry those. It is also possible that he is a D'Uccle cross. Which hatchery did he come from? Hatcheries breed for production and quantity, not quality. So, you end up getting birds that will resemble the standard (maybe) but not fit it perfectly. I ordered some chicks from a hatchery and ended up with single combed Wyandottes and crested Old English Game bantams.
Keep in mind that mille fleur is a color and not a breed.
Hatcheries will sometimes call mille fleur D'Uccles "Mille Fleurs" and porcelain D'Uccles "Porcelains". Those are actually color varieties and there are other breeds that come in those varieties but are most common in D'Uccles. It's similar to hatcheries calling EE's Araucanas or Ameraucanas.