Fluent speakers of English, could you help me with my English?

I am translating a very complex book about architecture and there are phrases that I find difficult to understand. Could someone tell me if the sketch (showing that above the sixth floor one lost all contact with the ground) was produced by Team X or by Smithsons? I find the wording confusing:

For all that Team X were committed to the multi-level city – an idea stemming via Le Corbusier from Hénard’s visions of 1910 – it was to the Smithson’s credit that they remained conscious of its limitations and in consequence produced one of the most critical sketches of their early career, namely a drawing which demonstrated that above the sixth floor one lost all contact with the ground. While the Smithsons were to use this sketch as a way of justifying a megastructural approach, their recognition of tree height as an experiential limit may well have exerted an influence in the 1960s on the general adoption of “low rise, high density” as the preferred policy for family residential development.