That isn't always true, for longer wavelength in particular it's very feasible to use many smaller telescopes with interferometry to reach effective aperture si

That isn't always true, for longer wavelength in particular it's very feasible to use many smaller telescopes with interferometry to reach effective aperture sizes we could never reach with a single telescope. However in regards to JWT I expect that a lot of its missions will collect miniscule amounts of light, making interferometry infeasible.