stencil bug with alpha diff painting mode

[Peter Wassink]

some weird behaviour... the alphadiff blend mode partly ignores the layer stencil.
the alpha diff tool strokes are still visible within the boundaries of the stencil.
i have 3 different alphadiff tool presets and one respects it while the other 2 don't
bug or other explanation?

the main difference between the 3 tools is in the wetprofile.