Actually, correct spelling means a great deal.
If you had not LEARNED the words and how they were spelled, you would not have progressed to the gestalt-recognition of the same letters in a somewhat-scrambled but still properly delimited (first and last) order.
This just shows that once a person has learned to read well, he is no longer parsing at the per-letter stage. Replace:
it dseno't mtaetr in waht oerdr the ltteres in a wrod are
With the equivalent trick, keeping first and last letters unchanged but making very near phonetic substitutions and word length changes by doubling or not doubling some letters (and I'll even not cheat, keeping my phonetic substitutions together like "uh" for a short e preceding an r):
it de'nzut mautr in wut oduhrr the lruhtes in a wred are
And you likely would not have gotten it without seeing the original. Of course the above example has lots of 2 to 3 word letters that don't change for syntax-recognition as well....a learned reader doesn't just comprehend at the per-word level but at the phrase and sentence-structure level as well. Which is why about the first things cryptologists do is break things into uniform size substructures (e.g. XXXXX XXXXX XXXXX XXXXX vs. XXX X XXXX XX XXXXXX) besides all the substitution games.
So spelling mattered - it trained you to recognize and parse language even when words are misspelled, not instead of having learned how to spell.