Yes, that video is incorrect.  At 4:55 when she said that her "tax advisor" told her to reduce the basis in the replacement vehicle by the amount of the gain on the relinquished vehicle, he was advising her to do a 1031 exchange, which is not allowed on vehicles exchanged after 2017.

In the video's example the gain would be taxable, and the basis would be the purchase price.

In your situation the loss is deductible, assuming all other requirements are met.

https://www.irs.gov/businesses/small-businesses-self-employed/like-kind-exchanges-real-estate-tax-ti...