Well, that’s the only way phonetic spelling can work. English used to be consistent between spelling and pronunciation, but the pronunciations were very different and spelling also varied enormously. There’s always been that drift, even before it was English (see the Saxon runes, etc.*). Having standardized spelling is what screwed up English in the long term - pronunciations continued to differ and change, spelling didn’t.
*The Saxon runes were interesting because they were phonetic but the letters didn’t have names - each rune was named after a word that began with that letter. (And in fact the characters could also represent those words.) E.g. the rune with the “m” sound was “man,” and you could use the letter both as the “m” sound and to represent the word. (And also replace all instances of “man” within a word as well.) So the pronunciation of the letter equivalent to “a” would be locked to the pronunciation of one particular word, unlike the modern “a” that can represent many sounds. Inevitably, of course, the pronunciation of those particular words shifted, screwing up the letters - because now there wasn’t a letter that had the sound it used to represent, and if the language still had need of that old sound (as it usually did), the whole alphabet needed to be revised.
