“Isn’t this very adenovirus vector approach developed through an inherently gain of function process?”
There is a difference between genetic engineering and gain of function. All gain of function is genetic engineering, but unless it gives a virus new abilities it is not gain of function.
Adding an extra protein to trigger an immune response, as in the J&J vaccine, does not enhance the virus in anyway.
“It is widely reported that JnJ modified an adenovirus that previously only infected monkeys,..”
That is gain of function into the human pool.
Anything added that causes the virus to do something ore than it naturally would do enhances it.