Numbering by player is not always correct. As per Gould (page 531 in Behind Bars), the last player is usually the first two double. If there’s three flautists and two are doubling piccolo, Flute 3 = Piccolo 1 and Flute 2 = Piccolo 2.
The except is when two players both double the same instrument. In this case, they keep their player numbers, e.g. Clarinet 1 = Bass Clarinet 1 and Clarinet 2 = Bass Clarinet 2.
Ideally, Dorico should eventually provide greater control for the automatic numbering to cover the cases above.