Could "a" be a ligature?

[Bluetoes101]

Where does EVA-a actually add information? The best answer I can come up with is this: in the vast majority of cases, the only information provided by [a] is that [o] wasn't chosen instead. And the o-cases tend to be rarer.

When you see "a" you can be quite sure "k,t,f,p,d" will not be next, this is not the case for "o"