User blog comment:Xilinoc/Ch. 666 (NOT YET RELEASED)/@comment-9282993-20160317113347/@comment-1338810-20160317155936

I assumed Urahara meant that when an Arrancar enters Resurreccion, their reiatsu changes from part-Hollow (having been in the humanoid Arrancar form) to full Hollow, which is in line with how we've been told Resurreccion works.