I believe that this answer, violates a basic condition of the puzzle and is therefore not a valid answer. Should we, as a site, allow answers to these kinds of puzzles that contain blatant "cheating"?
The answer is perfectly correct given the rules in the question.
The real question is should we allow the question?
The most popular opinion (which I share) seems to be no, that questions with multiple different answers should be considered off-topic and closed. Therefore, we don't need to worry about "cheating" in this manner.
An answer that “cheats” is wrong. The proper reaction to a wrong answer is to downvote it, not to delete it.
Your example illustrates why we delete low-quality answers but let wrong answers stand: it implies that we can accurately and authoritatively determine whether an answer is wrong. Let me quote the example here in case it gets deleted:
Let's say you have a bottle with a small coin in it and put the cork back in place. You have to remove it, but without take the cork out of the bottle or breaking the neck.
Push cork into bottle. Shake upside down. — kaine
Cut a hole out of the bottom. It's not breaking the neck! — Kevin
I don't see how you can claim that this answer “violates a basic condition of the puzzle” or “violates the spirit”. What is the basic condition or spirit that is being violated? The puzzle asks about a somewhat contrieved situation inspired from real life and is careful to provide enough information to enable a particular solution, but not so much as to make that solution obvious. It is an inherent risk that the puzzle will accidentally allow other solutions. Who has authority to decide which answer is “the” correct one?
I can't find any intrinsic feature that distinguishes Kevin's answer from https://puzzling.stackexchange.com/a/570. There is of course a distinguishing extrinsic feature — that one of them is one I haven't heard before whereas the other was a tired old thing before I was born. But inventing new answers can hardly be said to violate the spirit of a puzzle: on the contrary, finding creative answers is the whole point of puzzles!
If the question was a different one — if it asked “what is the classical solution of this old puzzle? history” instead of “what is the solution to this puzzle? brainteaser”, then kaine's answer would be correct and Kevin's would be wrong. But as things stand, Kevin's answer is not only perfectly legitimate but arguably better than kaine's. And you still haven't put forth any argument why it should be deleted.
Now the fact that we're arguing about what constitutes a proper answer to this question suggests that the question is not appropriate for Stack Exchange. Well, I think that asking a puzzle in challenge fashion should be off-topic (this is a site for asking about puzzles, not for asking puzzles), and that goes double for situation riddles and the like.
The problem is that "obvious" cheating is in the eye of the beholder. One person might think an answer is blatant cheating while another might just think it's very clever outside-the-box.
Questions with so much wiggle room for subjectivity and yet still require one specific answer from the asker are probably a bad idea for the site.