I got hit with that question today and was quite curious. Does anybody know the reason behind alternate vintage labels on Domaine Leflaive's vintages?
A quick google search even shows that both Batard and Chevalier can be found with both labels.
I can guess that if one of the bottles was labelled several years later, the design has changed .
This is also a guess but it also might be that one bottle was originally destined for export and another for sale in France. And somehow the one destined for sale in France got exported. It's kind of a weird thing I've seen a few producers do but usually for mass produced rosés rather than Grand Crus.
You’ll see that in places like Alto Adige with a producer doing a Pinot Nero, a Pinot Noir, and a Blauburgunder labeling of the same wine for different markets.
I think Zareh’s spot on on this one. One went to market at release and the other set as a shiner in the cellar for a few years, then got the updated label when it finally went out.