inverse The alpha channel just doesn't work with certain (some, or all) blendmodes enabled.
The alpha channnel does not work [normally] with blendmodes other than
BlendMode.NORMAL is the only one that treats it normally. All the others do something odd; you can see exactly what they do here. It's worth taking the time to understand exactly how it works as you then appreciate how useful it is, but also how limited.
There are two things in particular to bear in mind. The names are only a guideline, matching the names of effects in graphics packages like Photoshop (or the classic Flash API) that they most closely correspond to. But unlike such software they are inherently limited by the hardware, and so do not precisely match what's possible in software.
And many depend on treating the source and destination differently (from
.NORMAL). So they require the source and/or destination to be set up in a particular way. Some only work in a