I agree that an instamine isn't exactly the same as a premine but when 35% of the outstanding coins were created in one day that is highly significant. I'm not sure that one day gap really makes that big a difference compared to just issuing 35% of the coins in the genesis block. It's certainly worth noting somehow anyway.
By that definition, practically every PoS coin out there was "instamined". Most are 100% mined within a week.
Not if that was the published distribution schedule. Fast, yes. Dumb, maybe, but not an instamine.
Dash did not adhere to the published schedule. At all. First of all the difficulty didn't adjust properly due to a (alleged) bug. Second of all the number of coins created was too high due to a (alleged) bug (and the extra coins were not returned the way they were with Bitcoin). Third of all, the future rewards were arbitrarily lowered after the instamine.
That does not apply to "practically every" anything, other than "practically every" instamine scam.
There were two main issues at launch. A LOT of mining power was pointed at the coin (probably because it was the first coin to use x11 and therefore for which you could actually use your CPU to mine it) yet 1) the difficulty readjustment was infrequent and 2) limited to 4x the previous difficulty (both common protections against "stalling" new coins at impossible difficulty levels). These protections allowed a huge number of blocks of significant size to be emitted before adjustments could take place. So yes, lots of coins were emitted at a faster rate than planned. That's a long ways from a fraudulent instamine.
Instamines or premines certainly aren't necessarily fraudulent (in the sense of deception) at all, so it doesn't matter. If coinmarketcap thinks it is important to let its users know when a huge portion of the coins were mined/created on the first day, then they should. (I disagree with your characterization as to their not being deception here, nor did you address the issue of extra coins, as explained elsewhere, but it irrelevant.)
The coins from those early addresses were mostly transferred to exchanges and redistributed within weeks
That is also entirely irrelevant to whether the coin was significantly premined/instamined.
Finally, the reduction in rewards was not arbitary, and at that point what difference does it make anyway? Any emissions from any coin simply dilute existing holders. Emit half as much and you dilute existing holders half as much. LOWERING of emissions is a GOOD thing for existing holders of a coin
Exactly. Lowering the emissions benefits those who participated in the initial instamine/premine and makes the magnitude of that instamine/premine far more significant. Hypothetically, if you premine an arguably-reasonable 5% and then cut future rewards by 90%, suddenly your premine is now 50%.
So yes it is highly relevant information with respect to the context of the existing supply number.