Spanwise flow is stronger in the boundary layer, but to me it's kind of counterintuitive because the BL flow is slowed down by friction, experiencing less of a pressure gradient over the wing, therefore being decelerated less in region of pressure recovery. Wouldn't this make it so there is less spanwise flow in the boundary layer? (Especially considering that the BL thickens as it passes over the wing)
Answer that might help convey what I am trying to ask.