Is frame blending handled in linear color, or in the clip/timeline color space?

Also, even if color space between clip and output match, whether blending is done not based on the pixel values, but on the values transformed into linear intensities. Like for example, in HDR, if you have a 10,000 nit pixel, and you blend it halfway with a black pixel, that pixel should then be 5000 nits. But if you are blending in the PQ space, then that pixel would be about 92 nits instead. Obviously, a pretty major difference. It seems when I drop opacity to 50%, that this transformation is happening in PQ space rather than linear nits, so my guess is frame blending is probably doing the same thing, but I don't know for sure.

I have a project where I am blending many frames together from a very high frame rate source to a lower frame rate output to essentially create a virtual motion blur, and if the intensities are not blended linearly, then this motion blur won't look quite right and I may need to come up with another solution. But frame blending is Premiere is very fast on the GPU, so I like it as an option.