The SRC_IN and SRC_OUT blend modes create problems when used in the Blend effect and the Node.setBlendMode() API because they can erase parts of the underlying buffer where they have zero alpha. This causes problems with blending rendering primitives against each other since those primitives will have zero alpha everywhere "outside" the primitive and so they tend to cut a rectangular hole into the background which is neither pleasing nor does it make sense to the programmer.

These modes are also of questionable value as blending formula and so their absence until (if) we can come up with a way of implementing them so that we can distinguish between "zero color alpha" and "zero shape coverage alpha" should not be a huge concern.