Federal Taxes: Tax Impact of Volunteer Mileage Reimbursement at Standard Business Rate

There was another thread that discussed the tax impact of reimbursing volunteers at the current standard business rate instead of the volunteer rate. The consensus was that the difference was not considered taxable income.

I'm curious then what folks think about how WI and MN guidance should be viewed for other states. Additionally, I found an old article on Congressional Research that referenced it.

Federal Taxes: Tax Impact of Volunteer Mileage Reimbursement at Standard Business Rate