Sorry but that reason for a change feels very coercive. If cat 5 is intended to be total destruction, meaning that anything above the lower bounds for a cat 5 is indistinguishable, there should be no 6.

That's not what this is. (The person you're responding to didn't read the article.) They're not looking to add a "total-er destruction" category; they're looking to replace the current scale with one that takes into account more factors than just wind speed, such as storm surge and flooding. Under the current scale, a category 1 hurricane can be deadlier and more destructive than a higher-category hurricane. They want to use a different scale that better indicates the dangers. It goes up to 6 when multiple factors rate 5 on each factor's specific scale under the proposed system.

I think the title of this article is misleading and clickbaity. :/

Total destruction could be “total human-scale destruction”.

You could have “geological changes” above that; reroutes rivers, moves mountains, etc.