When a coin is born, if the initial difficulty to get a block is too low, you can get a ton of coins (blocks) really fast if you get in early. The coin is instantly mined.
Similarly, when a coin is mined to almost completion in a very short period of time some people consider it's been instamined as well.
But it's not accurate to state that any coin is "insta-mined" just because it's POW or POS mining period is say much shorter than another coin(s).
In fact it may well be that only coins that never are allowed to be fully matured could be termed even remotely "fair".
Or at least only ones that take at least many centuries, if not thousands of years, or maybe much, much longer.
We can take this very far out to infinity, but what's the point? That would be truly fair, but ultimately maybe UN-adoptable, especially in this 2nd Gilded Age of Fraud & Greed.
Toss in the benefits of POW/POS hybrids with their post POW minting (mining) through POS minting (interest earnings) after all the POW mining is done, and well for holders of those POW/POS hybrid coins suddenly those are extremely attractive and much like earnings (interest) on Bonds or savings accounts. And well suddenly field of viable Crypto-Currency competitors has increased greatly.
Yet lately we have had to endure FUD, and much worse being spread by a very few malicious types, and maybe some well meaning ones mis-informed too, tough to say. About how for whatever reason's those alleged inferior types will fail too, due to a not well thought out set of fundamental. Maybe not! lol...
In fact the inferior ones will certainly fail, especially if not tweaked to be made much more viable if need be.
Fact is inferior types of Crypto-Currencies will ultimately fail. But not the Superior types. POS types, and POW/POS hybrids will likely prove just as good, if not better than simply the very first POW types. Much to the dismay of certain types. It wont prove difficult to configure minor tweaks to solve any shortcomings is what I getting at.
On that Note:
Certain ones just can't seem to stand for any real broad Competition. I refer to them as the "challenged type" because just like the greedy, seedy, and ever fraudulent J. Paul Getty he couldn't stand Competition either.
Caveat emptor - let the buyer beware!