It's not really pompous. Fund 'vintage' is the way that VC firm partners (GP's) have to orient their thinking because it's how their investors (LP's) measure the success of a particular investment in their firm. The term vintage has been standard fare in this world for a long time, even if it draws its roots elsewhere... See also: 'carried interest'[0], which draws its origin from shipping centuries ago.

[0] https://en.wikipedia.org/wiki/Carried_interest