Commented this, but thought it might as well be an answer.
Couple things in regards to your questions and comments on Sumwun's hidden post (am chinese, but not born mainland, so could be wrong);
IIRC we do express translations pretty literally, 心金 is indeed the translation for HeartGold and SoulSilver is 魂银 (at least this is a common enough that we do refer to these like this colloquially). Same with Black/White 2, its literal, and I think 黑白2 is used, not even the character 二.
As to whether you can purchase these on TaoBao I have no clue, I just looked at it and couldn't find any apart from USUM/SM but maybe I'm dumb. I think its pretty common to just run emulators or R4s. The only cartridges I've ever got from China were dodgy bootleg ones from some chinese stall years ago tbh. As I said, I didn't actually live in China so my experiences are from travelling/being dragged by family/cousin's childhood, som y understanding and grasp of chinese isn't perfect.
In regards to your "SM/USUM" aren't as literal as you'd expect, they're pretty literal
精靈 is the only weird part, and it refers to to some mystical-elf-fairy-thing (it translates directly translates elf in english but it really isn't lol).
寶可夢 is Pokemon
究極之 is Ultimate but doesn't typically mean anything in Mandarin. Phrase dedicated to Pokemon essentially.
日/月 are Sun/Moon
You could easily just search for 究極之日/月 and you'd get the same results as the full name.
In regards to why this is different to our expression for Sun/Moon, which use 太陽/月亮 as opposed to 日/月 , which I think historically, mean pretty similar things, but 太陽/月亮 is the one that you would probably use/learn by default for Sun/Moon now. 日/月 are bounded by other meanings/chinese grammar I think, I'm not too sure.