coinmarket means nothing to new coins.
i can buy the first coin at 0.0001 of your coin@100 btcs. aka 0.01BTC total and coinmarketcap will take this 100btcs /coin rate and time it with your total coin and give you a marketcap of $100,000,000,000,000,000,000
You are right but that tends to work itself out in a couple of hours.
The main issue here is the same with all pre-mines where the pre-mine is withheld until some later date (Karpeles, Aurora, etc)
coinmarketcap multiplies the current price by the number of coins that have been produced so far.
Normally this is fine, but with a 50% pre-mine only about 1% of the coins may be tradeable, leading to a high unit price per coin.
coinmarketcap multiplies this number by the total coins in existence, say 51%.
So yea, the market cap is completely wrong in this case.
Really coinmarketcap should not include the premined coins in its calculations until they are released and available for trade.
Although this would cause a crazy spike between when the pre-mine is released and the price adjusts, so I guess it's messed up either way.