On smaller sites it is possible for suggested edits to sit in the review queues for very long, so there is scope for manipulating the suggested edits after only one review has come in but before it gets approved/rejected. For instance, suggested edits on Music Fans SE take 48 hours on average to be fully reviewed. This is enough time for changes to be made to a suggested edit between approvals/rejections.
I have actually done this when I noticed that my suggested edit could do with some minor improvements. For example, consider this suggested edit of mine to a tag wiki on Music Fans Meta. I didn't notice that it contained a broken link when I submitted the edit. After it received one approval, I changed the broken link and noted the change in the edit summary — but, the first approval still remains. Now, the approver has no way to know that a change was made and that they approved a different version of the suggested edit. (I don't know whether the original version of the suggested edit is even saved anywhere for comparison.)
This is far from ideal. If a change is made to a suggested edit after it has received a vote, then that vote is meaningless: it is for a different suggested edit compared to the final version that is approved/rejected.
Feature request: Any updates to a suggested edit (by the user who suggested it) should reset any votes on the edit.