When you sneak in old world type 16 blocks away from the border you just slip right off the edge of the block

steps to reproduce
1. go to world border in old world type and make a pillar
2. go to top of a pillar and use sneak to not fall off the edge
3. fall off the pillar

Observed Results:
you fall off the edge of the pillar when using sneak to not fall off the edge

Expected Results:
sneaking on the edge should prevent you from falling off the edge