Let me clear this up.
On FMH you can load a maximum of 4 countries and with this it determines your players. For example loading just England gives you more youngsters and a less spread of players compared to loadinng England, Spain, Italy and Scotland.
It isn't always the case you will get ALL the youngsters in England by just loading England as you can get some Spanish ones too and visa versa, however it all depends on what you have loaded.
Oh and FMH doesn't have under 18s or reserve teams but do have a reserve slot but not any players from it (just the younger first team players such as Turnbull at Chelsea).
Eds, it kind of tells you how to unlock Bojan but not sign him though it was poorly worded and not actually that true due to some Chelsea players only appearing when loading Spain up.
Ollie, this is nothing new and this has been known since the start of the game (well if you want to be technical since the start of FMH2009 when the feature was introduced).