I think that the Boris quote needs to be enlarged so that it becomes clearer what he is saying:
“Without your ability to do things in a different way if you want, and your ability to do free trade deals, there is very little point in Brexit. ”
I read it as: If an agreed Brexit goes ahead, but leaves us unable to negotiate our own trade deals, then that Brexit would be pointless. In that case we would not wish to take the 'agreed' (offered) deal, but would be better just leaving the EU without an agreed deal.
Effectively he is just reiterating "No deal, is better than a bad (or poor) deal." And in this case "No deal" does not meaning remaining within the EU, but leaving with no advance agreement about how we would in future deal with the EU, in other words, on WTO terms.
"I think Theresa totally gets that.": Theresa May has already stated that "no deal is better than a bad deal".