True, but Japhet got to 25 and only ever made 18 appearances out on loan. He only ever appeared in a Spurs shirt 27 times. As a comparative, Devine is 20 and is already close to 50.
Some of it was injuries, but a big part of Japhet's trajectory was incredibly poor management by the club, and the revolving door of managers. They kept him around as he ticked that homegrown box in a time when we never filled the quota. Ditto KWP, and more recently Skipp. The GK situation is exactly the same with Whiteman and Austin who are now 25/26.
As for you point, I don't think the issue is now. For me, the problem comes after the age of the group we have now and you therefore will be right in what you're saying very soon. Phillips, Veliz, Scarlett, Devine, Craig, Abbott, Donley, Keeley are mostly in the 19/20 range. The one to perhaps worry about in our loanees is Matthew Craig (21). Then you look at our 1st team of Gray, Bergval, Odobert and assumedly Yang. They are very young.
We could have an overload of new Tangangas, KWPs and Skipps in about 2-3 years time. I hope this time we cut them loose and let them get on with their careers if they're not having a 1st team impact. Hopefully, they'll make us some decent profit for us to re-invest as well. Realistically, we won't see all 15 of our visible young talent make it at our club. I couldn't predict that number right now.
Here's a thought thought. Perhaps the position we find ourselves in now with youngsters becomes a permanent state. I wouldn't be complaining.