This may have been said explicitly already: the original question was about whether diffraction limits the gains to be made from larger format film, assuming that large prints are the end product. When photographing a real world subject onto film, especially in large format film, you're often facing a tradeoff between stopping down for depth of field, and the onset of diffraction. For example, on 4x5, most people would consider using f/16 to be fine, but at f/45-64 diffraction could become noticeable.
This tradeoff isn't as pressing for the enlarging stage because the film and paper are nearly flat, so you're stopping down to compensate for residual non-flatness and any lens aberrations, and there is likely no benefit to stopping down far enough to reach diffraction limitations. So most respondents assumed that the original question was about the taking stage, not the enlarging stage.