I completely understand where you're coming from. I was in the exact same situation. I too am bothered by Apple's refusal to communicate what they have on-hand in the store.
I am fully aware that Apple products sell like hotcakes and they don't want to disappoint a customer by telling them a product is there and then it is gone 2 minutes later, but they could at least add a clear-cut caveat that they do not hold merchandise for people and that it could be gone when people arrive. But if they at least communicate openly with the customer, then the customer can make an informed decision.
With that being said, I worked hard at this and can offer you some advice that might help. You might already be aware of these things. If so, perhaps it will help someone else.
- When you call an Apple Store, you will be routed to a centralized call system and not the actual store. Most CSRs will only read you the company line, but occasionally, if you nicely explain your situation and ask if the CSR can call several stores within your reach and check on stock levels, they might do it for you. If you have the patience, keep trying. Someone will eventually do it for you. After about 10 calls over 2 days, I finally got a CSR to call a bunch of stores for me. Be prepared to wait on hold for 5-10 minutes while they do this. In my case, there was still no stock at the time.
- There is a trick for getting directly through to the actual store when you call. Just say "Manager" at the first prompt. You'll get connected through to the actual store and you can try to work your magic from there. Again, it seems like the person at the store will not be willing to help you 95% of the time, but maybe they'll be sympathetic to your situation. You might have better luck trying to call at off-peak times, perhaps a couple of minutes after they open. People are usually less stressed and less busy at that time and may be willing to go the extra mile for you.
- If you own a small business or even have a legitimate part-time business venture, you can work through that particular Apple Store's Business Team. I was made aware of this by other forum members here and it was the golden ticket for me. (I am actually a full-time working photographer. It puts the roof over my head and the food in my stomach. Not much else though...LOL.) Working with the Business Team, I received over-the-top stellar customer service. They immediately called me to tell me they had it in stock and they held it for me until I arrived. They greeted me with the new MBP in a bag when I arrived. And they gave me there dedicated business line and email address for true concierge service. And I can honestly say it works: I accidentally received a 2-m USB-C to Lightning cable instead of a 1m cable so I emailed them and within 10 minutes, they overnighted me the correct cable. I was blown away by the customer service...
The good news is the configuration you want is the BTO configuration that all the stores are getting (in addition to the base models.) I would not drive 2 hours either without some kind of indication that they had something at least in stock, so keep trying and hopefully you'll get the answer you need. And in the meantime, I'll send good vibes in hopes you'll get that answer soon!