> Not really. There's no way to guess how many english words are pronounced based on the written form, unless you've heard it before. And of course the pronunciation may vary wildly based on region/country as well.

> The most telling evidence of this is the existence of Spelling Bee competitions in english language countries. The fact that hearing a word being spoken is challenging enough to figure out how it is written that it is a competitive sport, says it all.

That's two exact opposite things.

Languages for which you know how to pronounce a word just from its written form => you can have spelling bee competition there.

Languages for which you know how to write a word when you hear it pronounced => no spelling bee competition.

I'll take French as an example : if you see "o", "au", "eau" in a word you know how to pronounce it. There is one and only way. But if you hear "o" in a word then good luck knowing how to write it. So you got dictées (spelling bees) even if you can easily guess how a written word sounds like. The existence of spelling bee competition in the English world is not proof that the language written word pronunciation are a guess.