Andre, I have no dog in this fight. And I don't have any LF Nikkors in shutter, let alone either of the 90s you're wrangling about, so I can't ask the lens(es) myself. But I do have the catalog, and I think you've misread it.
Nikkor-SW 90mm f/4.5S Nikkor-SW 90mm f/8S
Covering power f/4.5) 80° (f/8) 80°
Covering power (f/16) 105° (f/22) 105°
Image circle (f/4.5) ø154mm (f/8) ø154mm
Image circle (f/16) ø235mm (f/22) ø235mm
The f/4.5er has the same image circle at f/16 as the f/8er has at f/22. Question of the day, does the f/4.5er gain image circle if stopped down below f/16?