Fed Standard is kinda one of those fanon concepts, iirc, whereas English as a language is referenced, and as far as we can trust our eyes, is used in signage and is the official language of Starfleet (at least the Roman alphabet is the official script!).So if the humanity of ST's future is really as multicultural as it's claimed to be, it should have a more heavily hybridized language than it does. Heck, by the 24th century there should be countless Vulcan, Andorian, and Tellarite loan words and grammatical features in Federation Standard.
I was speaking hypothetically. Obviously the conceit of the show is that they're still speaking our English, but in the conjectural case I was proposing, the standard tongue of the Federation would probably be only partially based on English, so I chose to call it "Federation Standard" instead for the sake of the hypothetical discussion.