Havara l'chaleik yatzas (Shabbos 70a)

The braisa quotes R' Nosson saying the source of the 39 melachos is from eile hadevarim and then R' Nosson says that havara was singled out to teach that you're chayav on each of the 39 melachos. Someone asked this morning if there was any connection between those two statements. I assumed that there really wasn't but then I saw that the Pnei Yehoshua explains that they are somewhat connected. He says that really R' Yosi fits in better with the pesukim. It makes more sense to say that havara was mentioned to teach that it's a lav and that's why it's written in that lashon. R' Nosson though says that it doesn't make sense to say that because the posuk earlier had just said that if you're over on a melacha you are chayav misa and that is the source that there are 39. So it's saying that if you are over on any of the 39 melachos you are chayav misa. It therefore can't be that havara is only a lav. So he's forced to say that it's was singled out to teach that you're chayav a separate chatas for each melacha.