The numbers make no sense.
They do. Look at Duda's support - it will come from PiS supporters and possibly Konfederacja supporters, with a very small amount from the PSL and Hołowina. Meanwhile, Kidawa-Błońska, Hołowina and Kosiniak-Kamysz are largely electable by each other's electorate. I can't imagine the average PO voter deciding to stay at home just because Hołowina or Kosniak-Kamysz made it to the 2nd round.
Duda meanwhile has firmly placed himself as the candidate of PiS, which will also sour some voters.
I only know for myself - I would have no problem voting for any of those three.
and Hołownia has no political backup whatsoever
True, but what did Kukiz have beyond a bunch of small town mayors in 2015? Voters seem to like their maverick non-partisan candidates in Presidential elections, after all.
Why am I not surprised that more people would be inclined to vote Biedroń than vote Bosak?
Love always defeats hate, after all.