The insurance company wouldn't care about the DMV - if you have RV specific insurance coverage and they can see it is/was an RV, they pay to replace what you have, up to the value of the policy. Conversely, if you have van insurance and it is titled as an RV, they will still only pay what the van insurance would cover. The same would apply to a conversion van, which would also be titled as a van but has higher priced furnishings and equipment. In any case, ask that question of your agent or other insurance company representative. Note the persons name and the date as well as what they tell you, in case there is ever a question in the future. Theirs is the only opinion that counts.
I figured the DMV would be reluctant to change what a previous title said. That's a no-no without a strong case that the previous one was wrong, and it is still a difficult thing to get changed. It may be that Tennessee doesn't have a separate RV category for their titles. Or perhaps they always use the VIN-designated category, which would always be a van for a Class B. Calling it a van is not wrong, it just falls somewhat short of describing the extent of the equipment installed.