Technically instamines are different than premines because of differences in esoteric coinbase origin stories.

Premines must be created by the devs, while instamines are slightly more democratic in that there could be any number of participants.  A well advertised instamine with many participants may be just a coin with an unusually large early emission, so they are not as necessarily centralized as premines.

In Dash's case, technicalities about genesis blocks aren't sufficient distinctions to make a difference, especially when the terms normally apply to coins that (accurately/honestly) pre-announce intention to have insta/pre mines (usually for funding purposes).

Dash's fiasco of a ninja-launch, featuring an "accidental" 33% of all coins ever going to the dev and a handful of insiders more or less right away, is the functional equivalent of a premine.

Dash conspicuously lacks a strictly and successfully mathematically defined emission curve, which is the basis for any legitimate Bitcoin-like e-cash/digital hard asset.

Dash is whatever Duffield feels like doing this week.  In the Evan's Gate cult, there is no social contract other than "Obey Supreme Master Duffield; He is our Satoshi."

Dash has nothing like BTC's 21 million coin limit, which makes it even more implausible that Duffield couldn't burn the instamine or relaunch with fair notice and a patch for the "accidental" instamine-causing "bug."

With Masternodes being sold as a HYIP, THE DARKCOIN FOUNDTION INC's entire cockamamie scheme reeks of malfeasance.