Myth. My mini has hooves that are striped like that and she has the strongest hooves out of all 3 of my horses... She gallops along loose gravel with no issues and doesn't so much as bruise.
If your worried about them becoming dry and/or brittle, then water is your best friend. Don't even bother with all the fancy products, most of them just waterproof the hoof, they keep moisture thats already there on the inside, but they keep any other moisture out.
During the summer when it's just incredibly dry out there and my horses hooves look dry, I make a puddle around their water trough each day, when they stand in it to get a drink, their hooves get moisture put back into them too.
One product I have used and liked was Worlds Best Hoof Oil though, my old mare used to get cracked hooves and that seemed to help a lot, but other than that, water.
R.I.P ~ Bubbles - 25yo tb mare - 13.04.2011 ~ 8:30am ~ passed away naturally and peacefully in my arms