Fastest journey....
Indeed it is. If you start on the 13:07, the earliest arrival via Didcot is later than via Reading because of the trains that skip Didcot on both services. But when it works, via Didcot is quicker.
But as I said earlier, in this particular case leaving Stonehouse at 1307 the arrival time at Bicester Village should be exactly the same (1527) regardless of whether you take the via Reading route suggested, and the price penalty for so doing (more than double
), or change at Swindon, Didcot and Oxford.
As you observe stuving, this appears to be incorrect behaviour in the
NRE‡ planner.