Naming the letters of a script that is not written in Latin characters is harder than it looks, and the sixteenth Syriac letter is the clearest case in the alphabet. Its Syriac name continues the old word for an eye; the sound it begins with is a pharyngeal that Latin letters have no sign for; and every scheme for writing it in English has had to choose between a diacritic that most readers cannot type, an apostrophe that most systems will mangle, and simply leaving it out.
The modern character standard needs a name that works in plain ASCII, without diacritics, unambiguously, forever, so it took the last option and recorded the letter as E. That name is now what most references, fonts and software show, including this one.
The same pressure produces other surprises across the scripts in this atlas. Mandaic asz is spelled with sz for no reason internal to Mandaic, only to keep it apart from as in a scheme with no diacritics available. Syriac letter names appear in half a dozen spellings across the reference literature.
None of this is a fact about the letters, and it is worth saying plainly, because a reader meeting the name E in a list of Semitic letters can reasonably conclude that something has gone wrong. Nothing has. It is a naming convention doing its job under a constraint, and the letter behind it is the one Hebrew calls ayin.