Why are the Production Xs are delivered before all the Sig Xs. Does this make sense ?
Yes, an issue. My explanation is that many of the Sigs produced needed some QC as they were the first produced. The QC and any replacement parts are time consuming/done by hand. As the QC issues are identified 'fixes' along the assembly line are instituted and the late Sig/early production models need far less QC time.
TM being a young company needs the revenue associated with quick deliveries each quarter. So, production Xs that have passed QC easier are delivered before some of the SigXs that are still undergoing QC.
This happened with the SigS/Production Ss as well. I certainly don't believe TM wanted to do it this way but it became necessary to meet quarterly numbers.