Is it true that high-heeled shoes good for flat feet?

Shoes don't solve or: Create problems. They make the best or worst out of whatever situation you were born with. If the shoes are appropriate for the activity, fit and feel comfortable, then it is a good thing. Shoes with higher heels put you in a more stable position, which isn't always bad, but the can do other things such as put stress on the lower back and cause a tightening or stiffening of the achilles tendon.

No but: A low heel shoe less than 2 inches can reduce strain on the calf muscle which can reduce force on a flatfoot.