In this case I completely disagree. He's in for over $4k. For that kind of money it needs to be done right in the first place. The OP shouldn't have to pay more money to have someone else to fix it.
op,
You absolutely want the knife, but you want it done right. Correct?
At the same time you don't want to come across as an nitpicky prick, and piss off the maker. Thus assuring he continues to not put the care you want into it's creation. You don't want him to just issue a refund and take it back either, or god forbid tell you the job is done, and piss off.
What you need to remember is that he is not doing you a favor by building this knife for you. This is a business transaction. He is providing a product for a fee. YOU ARE THE CUSTOMER. Not his pal. You don't need for him (or them) to like you.
My advice would be to call (not email or PMs) and speak to a live body. Be firm, but always courteous. Let him know that you really want the product, but you want what was agreed to when you commissioned the build. That includes the jimping, blade style, grind, etc. Show stock photos compared to yours. Offer to copy & resend the original email with all those requirements. If you feel that this isn't working then let him know that you posted the question here on BF and what the replies were. Send the link if you must.
Do not relent. If you do, I doubt you'll ever truly enjoy the knife knowing what a terrible experience it was having it built. I know I would resent the thing, and likely sell it at the first opportunity I got.
Best of luck and keep us posted. This could be very educational for others.