Nice of Gerwig to add that twist.
It was a perfect touch. For one thing, it violated the typical dramatic convention of author as omnipotent and unbiased observer - that the work itself must not refer back to any author or to the writing/filming process. Such violations always win me over (Fleabag being a perfect example) because they inspire a playful and creative collaboration between audience and artist.
I thought the film brilliant in all aspects but particularly stellar re Gerwig and Ronan.
And watching it, I did imagine farmerman and Streep in passionate embrace.