Soul speed doesn't work on slabs when jumping

The bug

When a player is on soul sand/soil normally, they can jump and retain the soul speed effect. However, if a slab (or potentially other partial block) is placed on top of the soul sand/soil, jumping will switch out the soul speed effect momentarily, which results in jerky field-of-view and movement.

This may be intentional behavior, as the player is more separated from the soul block with a block above than just the sand/soil itself, but it seems quite unnatural nonetheless.