At first glance, knowing how to spell a word and understanding a word should be perfectly orthogonal. How could it not be? Saying that it is not so would imply that civilizations without writing would have no thought or could not communicate through words, which is preposterous.
And yet, once we start delegating our thinking, our spelling and our writing to external black boxes, our grasp on those words and our grasp of those words becomes weaker. To the point that knowing how to spell a word might become a much bigger part, relatively, of our encounter with those words, as we are doing less conceptual thinking about those words and their meaning.
And therefore, I argue that, in a not too far-fetched extremum, understanding a word and knowing how to spell a word might not be fully orthogonal.
That sounds like setting-up your child for failure, to put it bluntly.
How do you want to express a thought clearly if you already fail at the stage of thinking about words clearly?
You start with a fuzzy understanding of words, which you delegated to a spellchecker, added to a fuzzy understanding of writing, which you've delegated to a computer, combined with a fuzzy memory, which you've delegated to a search engine, and you expect that not to impact your child's ability to create articulate thoughts and navigate them clearly?
To add irony to the situation, the physical navigation skills have, themselves, been delegated to a GPS..
Brains are like muscles, they atrophy when not used.
Reverse that course before it's too late, or suffer (and have someone else suffer) the consequences.