Not only with Unseen Forces. I do not discard the possibility that this can also happen with other expansions (mostly for Non-Japanese/Non-English) … and not only in Spanish. Can also happen with other languages.
About your question, I guess that the Non-Holo variant has been launched for all languages which Unseen Forces was launched (A theory I just have … I need to research that to have a near accurate answer)
Spanish ex era in TCG is really mysterious. Has lots of “unregistered” things. In the case of Unseen Forces 
, it’s difficult to find images. I’ve been trying to contact people who might have images to work on them in an attempt to preserve them all.
Yes, I totally agree with the part of little documentation you mention.
P.D: If I manage to find or if someone provides me information about Lugia Deck , I’ll create “a sequel” of this thread, but related to that specific deck. Also, if I find cards/products that might be unregistered on Internet and might be unknown for most collectors.
Hope you’ve liked the thread!!! 