I see that punctuation for acronyms all over the web, etc.
I see it as a way to distinguish between the acronym itself, and its plural, vs a new acronym, which could be confusing.
Another example is for items at are often referred to by a nominal size, such as 35" diameter tires are often referred to as 35's, and AA cells are referred to as AA's, and so forth. Its such a common usage that it would surprise me if it became an alternative way of expressing it.
I do cringe a little when I see it, but, I have decided that the context is always able to make it clear as to what is being communicated, and, for me at least, as long as we know what we mean, HOW it is expressed is OK.
When I receive communications from work, etc, I see what, to me, initially looked like code. A series of abbreviations and so forth that was confusing.