This seems to be a drive towards clubs having a reserve team competition.
But it seems illogical to me to keep the U19s but not permit older players to play in it. You need to have somewhere for the older ones to go.
There needs to be a reserve grade competition replacing the U19 one, with the acceptance that lot of players would of course qualify for U19s as well! (like they used to have)
If you are 18 or over reserve grade is in theory suitable