The idea that spending money in posh stores/suburbs, perhaps needlessly, is hardly financially sensible, and to get what? A $5k/yr card that is aimed at a high-end frequent traveller, which the author states he isn't? Spending more money just to own a card that isn't particularly coveted by the frequent travellers on this site (
here and
here) doesn't sound like a good prize at all.
As for paying tax, there's 700-odd pages
here about
not using your AmEx to do that. If it were a good idea, there'd be that many pages again. Plus, if you're wealthy/silly enough to not care about the surcharge, or not savvy enough to seek a better points earn, you probably care little for whatever monthly gift AmEx might fling you.