As @Leebo said, I don’t have a problem with the Japanese and I understand where it came from. It’s more about “muscat” being used so much in English in Japan that it makes you think it may actually be correct in some places (which as people have said, isn’t the case).
I think one of the big problems I have is that on google translate, マスカット translates to Muscat, which is probably a large part of why it’s used so much.
Meanwhile, green grape translates to this, which I can’t say I’ve ever heard.
I think some varieties of ‘muscat’ grape are red – the Japanese wikipedia article マスカット (ブドウ) leads off with a picture of red/black grapes.
It says that 日本では単に「マスカット」という場合は、「マスカット・オブ・アレキサンドリア」を指す場合が多い。 – and Muscat of Alexandria is a green grape.
For me (UK English), if you said ‘Muscat’ I’d assume you meant the wine (but it’s a sufficiently topic-specific kind of word that I might be confused if you didn’t use it in a context where a kind-of-wine word would be likely).
Oh I completely forgot about 白ぶどう! Yeah I’ve seen that quite a bit too, I want to say I’ve seen it used more in juices (as your picture would suggest).
I’ve definitely heard muscat used before in English… specifically to refer to muscat grapes. Actually, I think I’ve only heard “muscat grape” rather than just “muscat” by itself. (And even then, I think I’ve only heard it the once, several years ago on a family vacation when we stopped at a winery since my parents love wine and I got muscat grape juice.) We definitely just call green grapes “green grapes” though unless we mean a specific type
