I would only be permitted to fly it for six months in any year. This was plainly a lie.
Broom/IO...to be fair it's not neccessarily a "lie".
I do know that when I got my first (I had two) FAA PPL "issued on the basis of" (From Colgne/Koln FSDO), the FAA inspector asked me, conversationally, "Why do you want this licence?".
"Because I can, it was a fun cross country from Manchester to get it, and I'd like to be able to fly N registered aircraft if I find one.", says I.
"Oh", says inspector, "I don't know where you would be able to find one, because any N registered aircraft, in order to remain on the US register, must spend a minimum of six months from every year in Federal airspace - unless it's an international carrier on a scheduled route".
I used to argue the six months ruling, too, until folks found the "get around" of having the aircraft owned by a "US Trust".
Nowadays, it's so commonplace for folks to have N registered aircraft that it's probably too late to do anything about it, so nobody really cares any more - despite the eforts of Customs & Excise and the DoT.