When entering spectator mode while standing on the ground, the player moves down a bit, which makes you fall down

When entering spectator mode while standing on the ground, the player moves down by a bit. This is related to MC-146582, as it is considered a parity issue as well.

Steps to Reproduce

1. Stand on the ground.
2. Make sure the show coordinates game rule is on and take note of your Y coordinate.
3. Use /gamemode spectator to switch into spectator mode.

Expected Result
The player stays on the same Y coordinate.

Observed Result
The player Y coordinate position is lowered when switching to spectator mode.