Not sure why people are trying to fool themselves that Allardyce is something that he isn't but it's as clear as day that he doesn't trust youth. As
@bluestevon said about Koeman you don't just judge them over the course of a few months or even a single season, you have to look at their record over a couple of seasons before you can see if they really trust young players. We've got Allardyce's track record on the last twenty years to judge him on. It's not pretty reading.
Spot on, the single easiest way and one that works with fans is for a manager/any manager in fact to come in with a negative feeling amongst the fans and to start giving some kids a game initially, as it wins some over, Christ - a manager under pressure can sometimes cynically do it to try defuse the pressure on him, Martinez being a great example when then crowd had 100% turned on him, goes out next home game and gives two kids their début, immediately got the crowd back behind them and off his back for that home game if iI remember right.
No 'firefighter' manager regardless of what they spout out their gobs, will back kids, purely because they are always a short term fix for clubs and they know it, so they aren't arsed what comes later and building a better team going forwards, they are just about instant results.
Koeman for example - he never really trusted kids, he just had such an awful recruitment in charge that he had holes all over the squad which meant kids basically had to play as they had no other choices realistically, but he was in his mind never building 'a project' he just wanted to boost his rep with results for 2 years and then try to get the Barca job etc, Allardyce - short term 6 -18 months max, why is he arsed about bringing a player through who will have spells of inconsistency during that time before kicking on for another manager who follows on from him, same boat is
Moyes, Pullis, Pardew etc.