It seems like you are confusing tstart and tstop, but maybe I'm not understanding your concern.  The commanded states (and associated planned *commands*) extend up to the beginning of the backstop commands being reviewed ("backstop tstart").  So the commanded states required for model evaluation will *start* at the specified `tstart` (per my original comments) and typically *end* at 2099 (or whatever is the generic into-infinity time).  This includes the time up to the start of the backstop commands.

(p.s. I had a little trouble finding your comment, being as it is hidden in an outdated diff).