Ebay Guide: MATCHPRINTS Color-Proofing Test Cards! TCA (youtube.com)
I don’t know of an article on e4 dedicated to matchprints at this stage, but if there is one I’m sure someone will find/link it. I bought my Pichu, Pikachu, and Raichu (have since sold Pichu/Raichu) from an e4 user in 2015 or so who had purchased them from Rusty (TCA Gaming). As time goes on, it will probably be harder and harder to verify the authenticity of the “cards” given they don’t fit some of the standard molds for authenticity checks on Pokemon cards. This was a concern of PichuFan’s, who had decided to not seek the Pichu for their collection.
To this day we haven’t seen a convincing fake surface either though for them, to be fair (that we know of at least)