That response email is a canned response, either from a chatbot or an intern who knows nothing about aviation.

Bottom line, there is absolutely NO regulatory allowance for single pilot airline ops in the US (except for possibly very, very small propeller planes).

Some foriegn airlines are trying to get approval to eliminate a third relief pilot from long-haul crews who need to rotate for rest. The idea there is one pilot can rest in the back during cruise flight, while a single pilot minds the ship during the low-workload cruise phase. In the event of a problem, the other pilot would return to the cockpit. None of us like that idea, but there would be another pilot on board at least.

No US airline is authorized to do that either.