Why would S be higher margin now then the X. The S has always been more mature, but it should level off and the X should become just as mature now that all the issues have gone down for more then a year now. X got the same price drop as S last year. Also, counting vin's is a fools errand if you ask me. X is also higher ASP which is good for the top line as long as the margins are the same.. even if the S is slightly better precent, it could still mean more total margin for the same number of model X as S.
I remember pretty vividly the eoy last year when tesla was delivering X VINs in the 80,000 range. I was paying close attention because my x was on the last delivered in 2016 with a 32xxx Vin number. To me 50,000 model X in 2017 meant near parity with S. If you are saying that VIN tracking is only showing 90,000 for X, then we are in a dire place with model X that was acceleration. It would be like it hit a brick wall with less even half the cars produced quarter over quarter for a model that was growing for 10+ straight quarters. It makes no sense.