The whole 'two billion people can read the Arabic alphabet to some degree' is a weird claim. Maybe it's possible, but there aren't two billion people with functional Arabic literacy. Most Arabic is written without small vowels (harakat). You could have script that is justified right-to-left and with letters correctly connected and it still be gibberish. And many of those 'two billion people' would be none the wiser.
So, there are degrees of literacy involved, and what we're talking about here is one step up from the bottom layer, a recognition of the writing system, not of a specific language. I can muddle along somewhat in French, especially written French, but I have essentially no Polish despite working with more Polish people than French. Nevertheless, Polish is written in a Latin script (for about a thousand years) and so I…
No, reading and being able to decipher script is different. I can read portuguese, spanish or italian (even romanian) to some degree because the languages are close enough to each other but I can't read polish, basque, finish or magyar despite them using the same latin script