Seems like that would shoot the shit out of being able to read at any decent speed. You probably don't notice it (yet) because your ability to read is still so poor that you don't notice the extra second or so that it takes you to figure out what's written.
You essentially cut your reading speed down below that at which you can "speak". It's a very similar problem as to why it's so painful to input Chinese with a Roman keyboard. You have to figure out what tone it is, then you get a chooser to pick between all of the (sometimes lengthy list of) homophones. The homophone-space is incredibly small given the huge semantic space of the (any) language.
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