Whatever, I'd go with Lehmann's main argument:
Real poetry is an account in fancy words of something real, but it is a show, a rendition, a collaboration between what really happened and the artistry required to write a good poem.
Is poetry fiction? Yes, in a word, yes! Poetry is a story written up with artistic affect in mind. It’s not true in all the details, but it is true in all the important ways. Poetry is true to life, not necessarily true to the facts of the real events depicted.
this is not at all the way I see Sweeney A. I only have small observations to make but to the extent that Lehmann sees it in a particular kind of place - a course (sic) pub - and that the bamboo tree business is supposed to be a referential nod to any worldly idyll viz Gauguin's world. Well I can't see it. I know that the boys arrive and Doris calls down to them in the street but the notion that the play can be imagined in a setting is at odds with the irreal sense of space and time. And the Bamboo tree is more a link to the music hall than the actual South Seas. ( I think of Judy Garland in Meet me in St Louis doing the song by the way)