Is the year 1999 attributed to all cards from Japan's Neo 1 Pokémon an oversight? 0

[PichuCollector]

CGC has followed PSA and BGS to attribute the year 1999 to Japan's Neo 1 (Gold, Silver, to a New World...) set. On 10th December 1999 the Neo Premium File 1 was released in Japan, introducing the 9 cards which made up the generation 2 starter Pokémon evolution set (Chikorita through to Feraligatr), however the remainder of the set wasn't released until 4th February 2000 (this can be verified at https://www.pokemon-card.com/products/neo/).

I've attached a picture of a CGC-graded Pichu card from the set which I've cropped from an eBay listing. Pichu here was not part of Neo Premium File 1 and did not appear until the main set release in 2000.

Has 1999 been attributed to all cards from the set for ease of cataloguing or is this an oversight?

Edited March 4, 2021 by PichuCollector