Correct but if you have 13 cells in series all charging at x number of Watts, then it’s only reasonable to assume 10 cells at X Watts is going to take longer to charge a pack to 720 Wh’s than the 13 cells.
Totally lost me there.
The only way you can charge faster is to use more current. The original post suggested that a higher voltage battery can be charged faster.
The current limit is based on what the cells themselves can take. How many cells you have in series (the voltage) is irrelevant in terms of the max current you are able to use.
You can't charge a higher voltage pack faster unless A: the cells are rated to take a higher charge current than the previous cells used or B: the charger manufacturer chooses to push the current output closer to the max cell rating (which many chargers don't). Either way, it's nothing to do with voltage.