A Hexcrafter Magus at level 3 unlocks the access to Magus Arcana. Because of Hex Arcana, he can elect to pick a Witch Hex instead of an Arcana. PCGen does not allow me to pick a Witch Hex at level 3. The "arcana" Gain Witch Hex does not show up until level 4 where you now get a free Hex for trading out Spell Recall. So in reality, you can get a Hex at level 3(Hex Arcana) and another free Hex at level 4 (Hex Magus). If warranted, you could get 2 Hexes at level 3 by using an arcana slot and spending a feat for an Extra Arcana. Therefor at level 4 you could have 3 Hexes.
Gain Witch Hex states Requirements: all of ( var: WitchHexAbilityLVL at least 1, var: WitchHexAllowed at least 1 )
I don't know much about variable names but it should be related to being a Hexcrafter Magus the ability to get arcanas i.e. level 3.
Hex Arcana: A hexcrafter gains access to the following magus arcana, or may select any witch hex in place of a magus arcana. At 12th level, the hexcrafter may select a hex or major hex in place of a magus arcana. At 18th level, a hexcrafter can select a hex, major hex, or grand hex in place of a magus arcana. He cannot select any hex or arcana more than once.
Accursed Strike (Sp): A hexcrafter magus who can cast bestow curse, major curse, or any spell with the curse descriptor can deliver these prepared spells using the spellstrike ability, even if the spells are not touch attack spells.
Hex Magus (Su): At 4th level, the hexcrafter magus gains access to a small number of witch’s hexes. The hexcrafter magus picks one hex from the witch’s hex class feature. He gains the benefit of or uses that hex as if he were a witch of a level equal to his magus level. This feature replaces spell recall.
1) Create a level 3 Hexcrafter Magus
2) Try and get a witch hex instead of an arcana
3) You CAN'T get a witch hex [Gain Witch Hex]
4) Level up Hexcrafter Magus to level 4
5) You can now have [Gain Witch Hex] in the arcana list AND get a free Hex for trading out Spell Recall
Not intended function