That result cannot be realistic, otherwise, very long focal length lens systems would be fairly useless. In practice, the apertures of these long systems are reduced, more or less according to the empirical rule(2)Now a team of researchers develop a new photographical device that can resolve at 50 gigapixels: AWARE-2 camera(1, *).
And below there are some examples of its capabilities(1):
(1) D. J. Brady, M. E. Gehm, R. A. Stack, D. L. Marks, D. S. Kittle, D. R. Golish, E. M. Vera, S. D. Feller (2012). Multiscale gigapixel photography Nature, 486 (7403), 386-389 DOI: 10.1038/nature11150
(2) Adolf W. Lohmann (1989). Scaling laws for lens systems Applied Optics, 28 (23), 4996-4998 DOI: 10.1364/AO.28.004996
(*) I update the post with a page dedicated to AWARE, via MacBidouille forum