Pikachu and Raichu were planned to be released in the Plasma Freeze Three Pack Blisters, but due to the cancellation of an English Landorus Box, BW Promos Landorus and Druddigon were issued in the Blister Packs instead of Pikachu and Raichu. Because of this abrupt change in products, there was not enough time for this promotional card to be repurposed into a different promotional product and remains unissued.
This makes it seem that they were actually printed.
Taken from the Bulbapedia page-
"In Japan, this card was released as one of the BW-P Promotional cards and awarded to participants of the Pokémon Card Game Classroom deck building learning events held during May 2012. Those who had already participated in at least one session were awarded a Pikachu promotional card. Participants using that card in their deck in another session were awarded this card.
Pikachu and Raichu were planned to be released in the Plasma Freeze Three Pack Blisters, but due to the cancellation of an English Landorus Box, BW Promos Landorus and Druddigon were issued in the Blister Packs instead of Pikachu and Raichu. Because of this abrupt change in products, there was not enough time for this promotional card to be repurposed into a different promotional product and remains unissued.
On July 21, 2014, Pokémon.com updated their card database with images of all 101 BW Black Star Promos, releasing images of the two previously unknown promotional cards falling at BW77 and BW78. By the end of the night, however, the official site had removed any trace of the Pikachu and Raichu cards. They are still visible and available in the Pokémon Trading Card Game Online."
tl;dr they only exist in Japanese because of a last minute product replacement in the US @thymeee
These cards were going to be promos in English Plasma Freeze three-pack blisters, but were changed last minute to the Landorus BW79 and Druddigon BW80 promos because TPC believed those Pokemon would be more popular with children.
To make matters even more bizarre, the guy has deleted the 3 tweets.
Their bio seems to imply they’re wanting someone to buy their entire collection from them, so I’m guessing they’re trying to drive up hype until that happens?
Fun fact: whelmed and overwhelmed mean quite literally the same thing: “overcome in thought or feeling”.