The XYZ coordinates shown in the debug menu display the player as being +1 block on the X and Z directions, leading to possible teleportation inconsistencies. The accurate coordinates are however shown in the Block coordinates shown directly below the XYZ coordinates.

The picture included shows off the locations of the coordinates and where you teleport when entering in the XYZ coordinates.

Update: After some testing I have discovered that the inaccurate coordinates only occur on the -XZ axis. The block coordinates seem to only show -1 and not -0 as the XYZ coordinates above it show. causing this odd difference.