I don’t think Jared having a growth spurt is taking the writers by surprise and I think they have lots of story reasons to suggest he grew or to (as they did with Bailey and Dylan) pretend he didn’t grow, whichever they want to do. He’s grown a little from the pilot, but it’s not like he suddenly shot up and looks like a teenager (especially next to hollywood-style 20 year old teenagers cast for the Lost Boys like Felix) rather than a kid. They might not put him in a scene with the other kid actors he’s been in with before (like young August, Grace or whoever) but those kids probably grew too anyway. Long term I kind of wonder what they have in mind but actors growing is not a new problem.
“If I had a world of my own, everything would be nonsense. Nothing would be what it is, because everything would be what it isn't. And contrary wise, what is, it wouldn't be. And what it wouldn't be, it would. You see?” -- Lewis Carroll, Alice's Adventures in Wonderland & Through the Looking-Glass