Keep in mind that "European Cut" is just a Legere brand name for one variety of its Signature Series reeds for Bb clarinet. It's based on a soprano sax reed, so it has a slightly wider but also thinner tip than the regular Signatures. These are intended for French-style clarinet mouthpieces.
"German cut" refers to reeds from any company, cane or synthetic, that are designed to fit German system clarinet mouthpieces (generally narrower and less tapered reeds than those for French-style clarinets).
"French cut" refers to reeds from any company, cane or synthetic, that are designed to fit French-style clarinet mouthpieces, i.e., the type played by people on Buffet, Selmer, Yamaha, Backun, etc., clarinets. In other words, the dominant type of clarinet. The Legere Signature European Cut reed is therefore a kind of French cut clarinet reed.
Don't confuse "French cut" in the above sense with "French file cut," which is sometimes used to refer to any clarinet or saxophone reed with the top part of the bark filed away in a straight line, just below the vamp.