Use of the word premine here is a result of the perception that the mining that occurred before Steemit launched was highly exclusive.
Has the mined stake from that period created any issues? Definitely.
What would you call the stake mined from the period that differentiates it from the mined stake after Steemit launched?
somebody said ninja-mine and that should sum up. I don't get the question :( technically there was no pre mine, it's like saying that bicoin was premined, it was just mined mostly inhouse. As far as I understand te documentation here was so crappy, people couldn't mine, but I'm getting my info from that blog post on bitcointalk. I myself wasn't around back then, but you can probably check back all the posts from the start of the chain.