Wawe writes the semivowel w and continues the Semitic consonant behind the Hebrew vav, the Syriac waw and the Arabic waw. Ge'ez keeps the w. Most Hebrew reading traditions have moved the letter to a v, which is a change in the language rather than in the script.
Semitic words are built on roots of, most often, three consonants, with vowels and affixes fitted around them in patterns. That system works cleanly when all three consonants are ordinary ones. It works badly when one of them is w or y, because those two behave half like consonants and half like vowels and tend to disappear, lengthen a neighbouring vowel, or change quality depending on where in the pattern they fall. Grammars of Ge'ez, Hebrew and Arabic alike therefore spend a large part of their length on the verbs whose roots contain one, and call them weak.
So a letter that looks unremarkable on a chart marks the point where the grammar becomes irregular. That is a good argument against reading an alphabet as a straightforward inventory of sounds. The signs are of equal weight on the page and are not of equal weight in the language, and it takes a grammar rather than a chart to show which is which.
It is also part of why an Ethiopian church school teaches grammar as a stage of its own rather than treating reading as the whole of literacy. A student who can pronounce every sign in the fidel still cannot parse a verb whose root contains a w, and the traditional curriculum separates the two skills and takes them in order.