Zerwick-Grosvenor (A Grammatical Analysis of the GNT, page 336) understands hINA + subjunctive (John 17:3) to be/function as an epexegetical infinitive that explains hAUTH (the demonstrative), which = "namely (that)."
Cf. sec. 410 of Zerwick's Biblical Greek.
I understand Zerwick-Grosvenor to be saying that we possibly do not have periphrasis for the (non-epexegetical) infinitive at 17:3; however, while Rogers and Rogers understand this verse to be epexegetical like Zerwick-Grosvenor, they seem to allow for the possibility that it could be periphrastic for an infinitive that is not explanatory.
As I read Zerwick and Grosvenor further, I guess we could have hINA + the subjunctive mood as periphrasis for the infinitive, but that only seems to tell the reader how the demonstrative is to be understood. I don't see how the epexegetical use of hINA explains anything but how we might construe the demonstrative hAUTH.