That arrangement is primes. The other arrangement is sevens: 1 and 6 opposite each other, 2 and 5, and 3 and 4.

Both of them can be unfair. Assuming rolling high is better, when 1 and 2 are opposite each other, those faces could be slightly smaller and therefore have a smaller chance of landing on them. This is especially easy with hand-made dice, which are bound to be somewhat irregular.

With "sevens", 1, 2, and 3 meet in a single point. If that point is somehow heavier than the opposite point, you're more likely to roll 4, 5 or 6.

I think I'd actually consider the "primes" arrangement to be superior to the modern one. No idea why that switch was ever made.