Generally, if the sample turns a solid pink color you are fine. That might take one, two, three, or even four level Taylor scoops, depending on the FC level. Needing more than two scoops is quite rare, but it can happen at extreme FC levels. And, of course, the sample will never turn pink if there isn't any FC.
However, Taylor says to always add at least two scoops. I am not sure what the exact reason for that is. But I can think of one situation where it would make a difference. The test is designed to have more indicator (the powder) than there is chlorine, so that all of the chlorine, both FC and CC, is bound to indicator at some point (CC doesn't bind till your add the R-0003). If the CC level is very high, and you only use one scoop, there can be too little indicator when you add the R-0003. That could give you a false, lower than actual, CC reading. Of course this can still happen, even with two scoops, if the CC level is high enough. But CC levels that high are really extremely rare, which CC levels too high for one scoop are merely very rare.
Ben's kit tries to speed up the procedure by giving you a larger scoop, so that one level scoop is the same as two level Taylor scoops. The TF100 tries to speed up the procedure by suggesting one heaping scoop, which is about the same amount as two level scoops. It doesn't hurt to add too much powder, within reason, there is only a problem if you add too little.