I had not read your presentation of the new ultrathins when I wrote my comment in the SIHH thread below, so as I wrote there I completely share your disapointment about reusing the small 21mm cal 849 in the 38mm.
However, that being said, I think the new watches are gorgeous, an really in line with Jaeger LeCoultre classic style heritage (no more Rossi-EWC-style nonsense!)
just an illustration, the 1962 ref 262. As you see it shares obvious visual characteristics with the new grande ultrathin (although in smaller diameter and in central second version)
I reckon the need for a name for a line of watches, however I also believe that 'ultrathin' is not a really appropriate name for the 'grande ultrathin' new model, as ultrathin means... ultra thin, and a full rotor calibre somehow does not really fit with this definition.
Still, in spite of the name for the auto, and the too small size of the calibre for the 38, I like these 2 new watches !
(one last wristshot of the ref 262 to illustrate the 'heritage)