The best evidence for a loose translation can be found in Doctrine & Covenants Section 9, verses 7-8, which was a revelation received after Oliver Cowdery tried to translate and failed.
"Behold, you have not understood; you have supposed that I would give it unto you, when you took no thought save it was to ask me," the revelation states. "But, behold, I say unto you, that you must study it out in your mind; then you must ask me if it be right, and if it is right I will cause that your bosom shall burn within you; therefore, you shall feel that it is right."
If Joseph were simply reading the text off of a stone, that would be the equivalent of having "took no thought save it was to ask me." Translation required effort and intellectual engagement on Joseph's part.
It's also worth noting that D&C 9 is the only contemporaneous document that addresses the translation process directly. Most records used in support of a "tight translation" come from long after Joseph's death.