Off the top of my head...
Harry Stafford and Harry Stafford
John Aston and John Aston (only first team to do it)
Charlie Mitten and John/Charlie Mitten
Graham Bradley and Dave Bradley
Barry Welsh and Nicky Welsh
Brian McClair and Liam McClair...
I'm not sure on process/accuracy/criteria but Manchester United have 78 former/current youth players featuring in the English league alone. If you count other countries it's over 100.
Amad arrived after he turned 18 so he never played in our Academy system. Most people would have never seen him play any youth football, at least not live or regularly.
Comparing the two as 15-17 year-olds is therefore very difficult.
The whole 'let them know you're there' was certainly relevant to many defenders. You could list a whole bunch of those. However, there were plenty of cultured ball playing defenders who were also great in attack in previous eras. Your comment was...
Just picking the 1970's randomly...
Phil Neal, Brian Labone, Bobby Moore, Martin Buchan, Mick Mills, Colin Todd, Roy McFarlane, Viv Anderson, Dave Nish, Derek Statham, David O'Leary, Kevin Beattie, Derek Parkin, Steve Whitworth...all excellent...
Not sure about Fitzgerald, but he last played a full game against Arsenal in the PL Cup on 3rd February. Jack Fletcher was injured in a friendly match against Oldham a couple of weeks ago.