Homegrown players get given far far longer then a bog standard new signing. I am not assuming anything I am merely commenting on what I read and I see that academy players are bullet proof regardless of ability.
But isn't that because homegrown players tend to come through at an earlier age and therefore have a greater scope for development and need for experience than an average established new signing, as the academy/homegrown/U23 player is naturally further behind in their development? I think it's about age a lot of the time, not whether they are homegrown.
A lot of fans want instant success, from an owner who will bankroll an unsustainable club, down to the ability of the XI on the pitch and so don't have the patience or longer term view a manager in the secure position of Robins will. A start here and there, and a regular 20 minutes off the bench can be invaluable to a young player but there are times that might mean it's not the absolute best XI on the pitch.
The average fan would rather win 6-0 with the best XI than 2-1 and let a youngster get a chance to develop. Mason (appreciate he is not home grown) will be a much better player this season for his extended run in the team last year although there were games last season that Brown would have suited better, same for McCallum in his handful of appearances.
It's a fine balance for the manager but I love the reputation our club has developed for giving youth a chance and it is benefitting us a club in hidden ways in terms of who is joining our academy and even the quality of loans we get. It won't always work out, it might be a Billy Daniels and not a Tom Bayliss but until you raise the ceiling for these young players you won't know how big they can grow and players develop at different speeds.
