I think there is a fairly easy solution to your question. Ask the contractor for references or to see a recently completed job in your area that used the proposed aggregate specification. I am certain he can refer you to another completed project so you can see the aesthetic qualities of the paving. Most contractors use the same highway paving grade specified in your State. These specifications vary, but usually limit aggregate to a nominal maximum size between 3/8 and 1/2 inch. Larger aggregate requires more fine filler and can result in voids.
Personally, I would be reluctant to second-guess the “formula” for HMA, provided it conforms to accepted State Transportation department standards. You contractor does not mix this stuff, he has it delivered from a batch plant, spreads and compacts it. His control over the aggregate specification may be limited on such a small job. On the other hand, he may get a bargain price for material using recycled aggregate.
Within a few months of laying the driveway, you should sealcoat it. At that point the size of the aggregate will be mostly invisible. Best thing would be to follow up on references and look at completed work.
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