What's the difference between 74LVC1G74 and 74LVC2G74, finally?
It might have something to do with the lithography differences for identical advanced high-speed low impedance low-voltage CMOS specs.  ( e.g.  cross-licensing of lithographic files with TI) 

Yet in 2016 it was only updated for a name change when NXP (now Nexperia) was being considered with all its patents for purchase by Qualcomm for $47 billion bills.

74LVC1G74 v.1   2004 02 02
74LVC2G74 v.1   2005 11 03    

My guess is that although using different processes with same results, there may be some customers ( aerospace ) that were notified of the differences and for reasons not evident in the datasheet only matter to those customers.

Although in 2016 a TI employee explained erroneously that 1G had one output and 2G had two.