New False Son ability not unlocking

[Tycool08]

I got up to 41 spikes purely through growth (it took forever needing like 100 bison steaks and 70 infusions over 4 loops) and still even after completing a run i didn't unlock his alt ability for the spikes.

[Valler]

You need to get to 44, as it has a base 4 stacks. Also the Stone Plate lunar item is your friend for making it to 44 stacks.