Having a casual battle with friends, with no additional rules. I used swords dance and then used photon geyser. Damage was not boosted, dealt same damage as normal, although my attack stat was obviously higher. I tried with both dusk mane, normal, and ultra necrozma, along with testing the Z move light that burns the sky. All of the attacks appear to function as special attacks regardless of necrozma’s stats. My necrozma has higher attack before swords dance as well. Later, I a zygarde used dragon dance, and my marshadow used spectral thief. Damage was dealt, but stat boosts were not stolen. Tested as well on xerneas after geomancy. Does not appear to function under any circumstance. I am using ATLauncher to launch pixelmon along with journeymap. Playing on the server RED.PIXELMON.GG. Thank you for your time.

Thanks for the report. These are two separate issues, and generally it is more useful to us if different issues are posted as separate reports. Photon Geyser always being special was reported in the ticket below, which you can follow to see its status. Make sure to use the search function in the future to see if someone has reported your issue already.

https://www.pixelmonmod.com/tracker.php?p=2&t=13454

Spectral Thief is one of a number of non-implemented moves that therefore don't have their secondary effects yet.