Accounting rules are governed by FASB in the US. Two years ago, "FASB has introduced a plethora of new and revised accounting standards that are certain to impact automotive dealerships nationwide".
https://www.axiom-auto.com/wp-conten...tter-Vol17.pdf
I read the newsletter but did not find any specific guidance about revenue recognition of vehicles sold to dealers but not delivered to retail customers.
I am sure FASB has an applicable rule.