"While phasing ... and can move through obstacles and other creatures, but it must end its movement in an unoccupied space."
The way that it is written, you can pretty clearly tell that the intent was to say, "Hey, you can pass through walls and creatures, but you can't end movement in them."
If you try, you can find ways to read it another way. You can even argue from a technical perspective that you're more righterest in your argument that it should be read another way, but it really seems that if the technically righterest way to read it is another way, it was just sloppy writing.
Besides: PCs really don't want creatures to be able to end movement in walls. A creature with reach, phasing, and an attack that allowed movement as part of the standard action attack would be an autoparty kill if smartly played. Move out and attack and then hide back in the wall where you're invincible. Wait for party to end readied actions waiting to get you (they have to rest sometime) and repeat. You might also need tremorsense or some other way to know what the party is doing, but it would be nigh impossible to stop.