He did not want to The Hobbit and LOTR to be even considered apart in any way.
In one of his letters Tolkien explicitly states that he regrets deeply the language for adolescents he used in The Hobbit. Unfortunately I don't have the book with me, so can't reference more precisely, but it definitely is there.
This is somewhat partial answer to the question: yes, it can be inferred and/or implied from various texts that most of his works were "translations" from original manuscripts, but there was also a very specific decision on the kids' language used in The Hobbit, which muddies the water on the issue the OP is asking about.
Like I said, I don't have the book on me, but the passage was to the effect of:
"in retrospect language for children that was used in *The Hobbit" was a bad idea".