My DS7 has high visual spatial ability and memory, and he was reading words before two and Mr Men books at two. I would of thought that being a VSL would actually made it easier to read.
My anecdotal experience is that it does, and it doesn't.
Whole-word recognition as a reading strategy is particularly helpful at the beginning of learning to read in English, because a great number of our phonetic violators are basic words. At early reading levels, a whole-word recognition strategy works in every case, whereas a phonetic-based decoding strategy fails almost as often as it succeeds. In this way, whole-word recognition is easier and more conducive to early reading, because it's more effective. And yet it's also more difficult, because it takes time, effort, and repetition to build up that mental, visual dictionary.
When we're talking about gifted VSLs, getting them to put in the time and effort is not really difficult... it's usually harder to get them to stop.
The success rate for phonetic decoding increases dramatically once you begin encountering words with Latin roots on a regular basis... in other words, once you begin studying sciences at a secondary level.