Looking at tactics on p72, I can't see anything that says a unit must be in command of its subcommander to use his good tactics bonus.
A commander must be "in range" to "direct" one combat - which I presume means to use the enemy's poor tactics rating. An opponent can use the poor tactics rating only if the enemy unit is within command range of a poor subcommander.
But I don't see anything saying about needing to be in command of a good tactics subcommander. The box on p73 may, or may not, imply units need to be under command.
Do they need to be in command?
Cam