I agree in general and I'm probably guilty of overhyping young players at least a bit. Don't think I'll stop doing that any time soon.
For me Gray showed, particularly as a CB, both consistency and maturity last season. He started 35 games in total, 19 in the PL. There were some issues on show, he had his ups and downs as you say. But imo way less than should be expected for an 18 year old and one playing "out of position".
For me he went from "oh brick, we have an 18 year old CM/FB filling in at CB" to "oh cool, another chance to see Gray at CB, he'll probably do well".
If that was part of his learning curve and he steps up from here we're in for a real special player.