Hello friendly poster.So I don't know if I'm missing a knowledgable mechanic here,but it really looks like a but to of the players (my opponent and I).
It was a really funny experience so I'm not bothered at all, just curious to see how smogon handles that kind of situation ^^.
Thank you for caring,
Besides the detail that this post is mainly meant for the investigation of cartridge and not bug report for showdown (there's a different topic for it), the interaction you witnessed is however correct.
The mechanic you are missing is the peculiarity of Plasma Fists.
Plasma Fists applies the Electrify effect, making following Normal type moves become Electric type.
Whirlwind is a normal type move, and got turned into Electric type due to Plasma Fists, which was then blocked by Volt Absorb.
Hope that solves your doubts.