He can really pick and choose how and when he wants to do what bit of training. It just makes sense to move IS from 3 to roughly 6 by the end of this season because that makes him a more versatile player (just straight train only that for 6 weeks)
While a handful of folks don't see tremendous value in IS on a PG (such as in the guide that most new players should read), there are quite a few situations over a given season where a PG will take shots that are based off of this rating. It's no secret that if you look at most any NT's board (i've looked at about 4 just to make sure), they literally post that a player with 6-7 IS/ID as a U21 and 8-10 as a NT is going to go a lot further than someone who just has 2's and 3's. That isn't by mistake. Theres no way this particular player makes it into the U21 or NT, but that doesn't mean he can't build him with the same approach intact.
If it were me directly, i'd work on making this my flow+ defense PG after IS, because of the TL market right now. Guys that are two dimensional in both offensive and defensive areas as a PG (8+ ID, 8+ IS, ~10 JS & then better @ OD, PA, HA, & DR) sell for roughly 1.2M average. one dimensional offensively, two defensively sell for 700-800, offensive weapons cost 400-600 for the most part. So you can always supplement with more offense from the TL, cant so much the well rounded types.