I don’t mean right from the get go. I mean after you’ve gotten a combo down, would that help ensure you never drop it?
It might help build your muscle memory. That level of repetition always helps to ensure that you land the combo, even with the stress of a live match going on.
I don’t think it’s absolutely necessary. A lot of people time combos based on visual or audio cues that aid them. Alongside with being able to do a combo with your eyes closed, these cues help to make your combo accuracy a lot better, which helps.