First of all, you are correct: the aiming times in FMP are indeed different from the vanilla (Rifle: vanilla 80%, FMP 70%). After like 5 years I can't remember the change, but I probably wanted to make more room for sniper rifles.
Still, I don't think we're speaking the same language... Of course the actual action costs a certain number of TUs. What else would it be? And that number of TUs is a set percentage of your soldier's total TU. In case of the Rifle (in FMP), it's 70% of your soldier's total TUs.