Translations:Jump Cancel/29/en

From Minecraft Parkour Wiki

However, it wasn't until version 1.8.1 that the ceiling variant became practical, as the player would often glitch through the floor.
Indeed, in 1.8.0, The game would force the player to be set 2.4m under the ceiling (1.8m player height + 0.6m step height), even if a block was present.
As of 1.8.1, the stepping method never goes below the player's position, so the player can no longer get glitched into the floor.