My dealer was given 3 allocations for this year...and I'm #3. The 1st one came in about 2 months ago. # 2 and #3 (me) are stuck in status 1100. Your explanation makes sense for sure. I think the dealer doesn't want to explain it as you have for obvious reasons. In San Antonio, they sell a lot of trucks...but do manage to sell a fair number of Corvettes. I've been a loyal customer to them and don't want to cancel the ZR1 and switch to a high-volume dealer back east. I'll just wait it out. No road trips this summer as I sold my Z06 to my son in Florida. It's hard to be Vette-less.
A dealer can't tell you exactly when your order is going to be accepted by GM. They can give you a ball park idea depending on the type of vehicle and the allocation they receive (Chevy Malibu, vs Corvette), but they really can't give you any specificity - especially when it's a very limited production vehicle like the ZR1 - where only so much allocation was given out to certain dealers, and that allocation is only given once per month at the end of the month.
So you can see why, in the grand scheme of things - it doesn't matter how good of a customer you are to a dealership. It doesn't matter if you've bought only one car or fifty cars from them. The dealerships are at the mercy of GM when it comes to ordering vehicles and allocation.
If a dealership says to you: "yes! Just write a check for a $10,000 deposit on your ZR1 order and you're order will get placed ASAP. It usually takes 6-8 weeks between the time the order is placed to when it gets delivered to us!"...don't write the check and bring your business to one of the larger Corvette dealers who know what they're doing, receive a larger amount of Corvette allocation, and will tell you the truth:
"....yes, we will take your deposit for a ZR1 order. ZR1 allocation is given out once per month, at the end of the month. As soon as we receive that allocation from GM, we will place your order. Once your order is placed in the system, it takes 6-8 weeks from the time the order is placed AND accepted by GM to delivery of the car here at the dealership. We will keep you updated on your order in the system as its status changes from the time the order is placed, then accepted, and then built."
There's a little more detail that goes into it, but you get the point.