Many years ago I started sharpening my 6mm parting tool at a weird angle... well 35° each side this was under instruction for a particular cut it was being used on, I just carried on using it, my 3mm one was 25° which is I believe the stock size of a new one, though I have not bought one in a long time. I do have one of the Sorby fluted parting tools I seldom use for anything other than scraping micro bead patterns not sure what the angle on that is as I only ever hone the top (non fluted) to what it already is, my thin parting tool again I have no real idea it is a Crown one that came my way from somewhere I can't remember, but I have long ago ground that to 20° on the bottom angle and 30° on the top bottom angle is a short section that I can quickly touch up on a diamond file.
Perhaps it is cabin fever from trying to avoid that zombie flu outside my safe workshop, but today it sort of struck me that they are all different, as I seldom use more than one of them at a time they just evolved that way and I seldom take any notice. They all work, do the job they are intended for but I was just wondering what angle/s are yours and why?