I totally agree that the words 'strictly follow depth chart' is very misleading and ambiguous.
However, instead of arguing over the language, let's focus on the game engine for now.
Setting 9 player to get 1 player full 48 mins is the right way. But u need to make sure no players were set at reserve. Instead ur depth chart prob should hv been
PG/PG/-
SG/SG2/-
SF/SF2/-
PF/SF3(since it is at PF should be renamed to PF2)/-
C/C2/-
I know this because last season I was trying to train 6 trainees, and after weeks of trial and error I found that this is the only way to ensure all 6 has 48 mins (Which for me will be sending in 8 players with no reserves). But it is definitely risky as I lost some of the games I should hv won when my trainee got into foul trouble.