As my son first started doing showcases, I heard many surmise that only velo mattered and where the ball went didn't. I can't speak for PG; PBR rules our area. At least with our experience, accuracy DOES matter. For a few reasons.
1) each showcase attendee gets an online write up/Comments along with their measurables. While some states are better/worse than others with them, this is where accuracy is noted. If a kid has a cannon for an arm, but throws over a player or into the stands, it should be accounted for there. I've attended around 8 showcases put on by various orgs over the last year or so, but can't remember a single kid who had outstanding velo but the accuracy of Ricky Vaughn. I haven't seen one kid be able to work the system/fool anyone. Maybe a couple pitchers, but we all know that's different in 2020. If you have Vaughn-like accuracy but throw 95+, you'll be just fine - at least for a while. But I've yet to see a C who throws 79-81 down to 2B who has horrible accuracy. Or a guy fielding a ball at SS, who goes into a full wind up or throws a friggin' pulldown over to 1B. YMMV
2) ratings and rankings get a lot of hate here (and most of it is fair), but go take a look at some of the highest rated/ranked players who have high velos and watch some of their videos from showcases. Then let me know how many of those guys have accuracies that are a joke. Here's another angle. The top PBR INF velo in our state among 2021s is 87 mph. But the kid who hit that number is only ranked 77th (in a small state). He's a solid player, but owning that top number in the state is clearly NOT getting him undo love.
3) video of players throwing are uploaded for everyone to see. So any C who has a 1.75 pop time but his throws end up in the dugout, will be seen. His 1.75 pop time will certainly get him some initial looks, but once a coach sees his throw downs bounce 3 times on the way to 2B, that'll be the end of that.
I'm sure there are a select few examples where a kid has completely worked the system by throwing accuracy out the window, but I've yet to see one. But I'd welcome any examples that are backed up with proof.