To be honest, I can't remember ever seeing the word voltaic before playing it in this game!
I did, however, have a vague idea that voltic (no 'a') might be a word, so I tried playing it and got the inevitable 'sorry, not known'.
It was while checking the COD that I found, not voltic but voltaic.
I played that and was quite amazed when it showed as 'common'.
However, even though it contributed to a slightly fortuitous rosette, I still think it should be reclassified.