I was playing in the latest 1.13 snapshot, I ran the command /execute as @e[type=sheep,distance=..15] run tp @s ~ ~3 ~, expecting all of the sheep within 15 blocks of me to teleport 3 blocks upwards. However, the sheep teleported 3 blocks above me instead. I believed this is an issue with the tilde notation.

I confirmed this when I ran the command /execute as @e[type=sheep,distance=..15] run setblock ~ ~3 ~ stone, where a stone block was placed above me instead of above the sheep.

I hope this is not an intended feature as the commands should be running AS the sheep, so tilde notation should be with respect to the sheep.