I have a hunch (but no proof) that this Pixiv account is an art aggregator and not an actual artist. Other than this and the Hoshiguma/Swire post, the only other upload on their Pixiv is post #4135384, which is listed (and even has a signature watermark) under "jzdavid" and has quite a different art style. jzdavid unfortunately has no other artist links so I can't cross-reference.

I seemed to find the actual artist of this and the Hoshiguma/Swire piece here, but I'm not good enough at navigating Weibo to find links or anything else that may prove this hunch one way or another.