Should we reject the first offer?

Yesterday I posted that we received a buyback offer of $18,620 for our 2022 Leaf S with 41K miles.

We replied with a counteroffer of $21,500. This was based on money we recently spent on the car (registration and new tires) as well as... hey, why not see what happens if we ask for more money as compensation for the inconvenience that Nissan caused by selling us a fatally flawed product?

Here's the reply we got from Morley:

We offer KBB + 40% to remedy to all inconvenient. However, you can sign the rejection part of the letter and I will escalate your case.

The process is as follow: once the customer sends requested documents, we will then formulate and present an offer letter for your review, you may then accept or reject the offer. If rejected, I will escalate the case to another team, who will contact you directly and discuss any additional options that may be available.

At this point, we're thinking we should reject this first offer and possibly get a higher second offer. Yesterday someone commented that they did exactly that and got their $15K offer bumped to $24K. Has anyone else rejected the first offer? If so, what was the result?