Brentford did similar maybe 10 years ago and closed their entire youth set up, but re-opened it about 3 or 4 years ago.
Be interesting to see Watford do.
Whilst Spurs have an u21 side, most of the players stay there for 1 or 2 years after U18's before being loaned out - the players do get a development benefit from playing u21's for one or two years but playing in u21's more than that, if anything means their development regresses.