[RPG] Pathfinder Kingdom Builder: How big, area wise, is a hex

The text you cited says that it works "as per the Sleep spell." The Sleep spell has the enchantment (compulsion) [mind-affecting] descriptors (Pathfinder core rules, p. 344). So, yes, PFG/PFE will protect against it as described.

Edit: Don't forget that, in the Pathfinder version of the PFE/PFG spells, the mental protection only works if the caster is of the appropriate alignment/at DM discretion (i.e., if the victim has PFE, they are only protected if the witch using the hex is of Evil alignment).

This seems to be a case of the creature description being based on a development version of a spell that was changed before publication, but the bloody skeleton's ability wasn't updated to match. Or the design notes for the bloody skeleton read something like "or 0 hp on blessed ground" and the developer that actually wrote the text didn't do due diligence in translating that into the correct spells. However it happened, it's an error rather than a mysterious rules interaction.

Go with your gut, and change it to "the area of a consecrate or hallow spell". Pathfinder and d20 system games in general expect GMs to make their worlds believable rather than to slavishly follow rules into weird contradictions and twisted corner cases that break suspension of disbelief, so you're entirely in the right to change this in your own games. If you're a player in another GM's game, suggest the fix as a sensible thing to do, but leave it up to your GM.