Actually, I think I may have experienced this when I moved to the later OHII campaigns. I can say with confidence that I have never had a radar contact in SH5 at all, even in those late-war campaigns, with both of the first two (90 degree/360 rotating 90) radar sets. I've never played later than the second radar set in terms of dates/upgrades available.
Been a few weeks since I've had time to play (and I've been distracted by Dangerous Waters

), but would swear to not having any. Should be easy to test in a single mission, but it'll be several days before I get a chance to take a look.