Did you also test (an confirm this) with the built-in Adobe encoders encoders?
The reason is After Effects is a bit "special" in terms of colors.
- It treats colors as RGB (and not YUV) values. But most encoders require YUV data as input. That why a lossy color format conversion is necessary.
- Also when using the high bit depth (16 bit per color channel) export Voukoder Pro has to remove the most significant bit, because Adobe used it for something else. That's why it is actually only 15 bit. This is from the first version of Voukoder on. But it only applies to 16 bit data, and only After Effects.
Every thing I tried (8/16/32 bit, OCIO & Adobe Color Management) and VKP 2 works well (on same config)
Adobe's builtin encoder have no issue
*btw the pic i posted was rendered on 32bit