I thought that common squads could move x number of units and attack with any other x units, not necessarily the ones that have been moved. This is what the rule was when I played in tournaments years ago. I now am looking at the tournament rules on the Renegade site:
Activating Figures
When a player takes a turn with a Common Squad, they may activate a number of figures equal
to those pictured on that squad’s Army Card.● A figure is considered activated once it is chosen to be moved during its turn (even if it
moves 0 spaces) or chosen to be an attacker during its turn.● When a player attacks with figures from a Common Squad during their turn, they may
attack with a number of figures equal to the number of figures depicted on that Squad’s
Army Card. Figures activated by moving this turn do not have to attack, but the total
number of activated figures cannot exceed the number pictured on the Squad's Army
Card (unless they have a Special Power that allows them to activate more).● For example: There are three Arrow Gruts pictured on the Arrow Grut Army Card. A player who controls six Arrow Grut figures moves two Gruts during the Move Figures
step of their player turn. They are still able to attack with up to three Arrow Gruts during Action 3: Attack with Figures on the Army Card (optional). One of these attacks can come from a Grut that has not moved, thus activating it; the other two must come from the two previously-activated Gruts.
Activating Figures
When a player takes a turn with a Common Squad, they may activate a number of figures equal
to those pictured on that squad’s Army Card.● A figure is considered activated once it is chosen to be moved during its turn (even if it
moves 0 spaces) or chosen to be an attacker during its turn.● When a player attacks with figures from a Common Squad during their turn, they may
attack with a number of figures equal to the number of figures depicted on that Squad’s
Army Card. Figures activated by moving this turn do not have to attack, but the total
number of activated figures cannot exceed the number pictured on the Squad's Army
Card (unless they have a Special Power that allows them to activate more).● For example: There are three Arrow Gruts pictured on the Arrow Grut Army Card. A player who controls six Arrow Grut figures moves two Gruts during the Move Figures
step of their player turn. They are still able to attack with up to three Arrow Gruts during Action 3: Attack with Figures on the Army Card (optional). One of these attacks can come from a Grut that has not moved, thus activating it; the other two must come from the two previously-activated Gruts.