Jay, not quite.
For example Year zayin-ches-gimmel (last occurred 5757, will next occur 5784)is a leap year during which Pesach is tuesday and yet Pinchos is the first of the three weeks (as it usually is )and those the Haftorah for Pinchas is not read.
Pinchas is read before the three weeks when Shabbos hagadol is Metzorah (as opposed to Acherei)This occurs in leap years Years when R”H is Thursday.
You are right about Chu”l which is where I live so that is what I focussed on. In E”Y it is more common since in years when Acharon Shel PEsach is Shabbos They read Pinchas before the Three weeks