group vs string is just a convention for ease of quick communication.
doesnt' matter which you use.
the point of a conventional terminology, regrdless of how it comes about, is so taht the terms don't have to be reexplained in detail every time they are used.
to clarify this by example:
if more (most) people already use a specific way of using a term, and others come along and choose to use the same term differently, then unless they specifically explain that they are indeed using that term in a different way and how they are using that term, every single time they use it, then all of those used to the more common way of using the term will have a large chance of misunderstanding what is being talked about.
so if you were to say you use 5 groups of three strings of cells, then those already using group for parallel and string for series would "know" you meant a pack of 5 parallel cells by three series cells, though they wont' know specifically how you've wired it.
but if you don't mean that, and instead mean 5 series cells by three parallel cells, you would have ot explain every time you say it that you mean that, if the convention is to use group for parallel and string for series. otherwise those used to the convention will have to assume you mean 5 parallel by three series and communication fails and problems figuring out what's going on ensue.
another example would be if you use a to mean amp-hours instead of ah. its' not teh convention to do this, but vendors that sell but have no clue about batteries often do it. or use w intead of wh for watthours. they mean completely different things.
the convention is to use a for amps, and ah for amp-hours, and w for watts and wh for watt-hours. becuase a is a current and ah is a capacity, and w is a power amount and wh is a capacity.
so when vendors list their batteries as being 52v12a, then since they dont' explain what that means to them, every time they list it, then anyone using the normal convention will assume they are only capable of outputting a maximum of 12a, and have no way of knowing what their capacity is. but they also have to wonder if the seller really means 12ah, not 12a...but they can't know by reading the listing because the convention is not being used.
if instead the vendor simply uses teh convention, then 52v12ah means they are 12ah capacity, and one can guess based on common cell types that it can do at least 24a, possibly a lot more. but at least one definitely knows they're really taling about the capacity and not the max current rating.
so you can use any word or term to mean whatever you want it to mean, but if you use it differently without detailing the rest of your usage, those that have learned to read it one way will have to assume they should still do so, and will misunderstand what you say.
choosing to follow the most-used convention of how a word or term is used results in the least amount of misunderstandings.