That's how you get a situation like the Gaza Strip, where Hamas is in charge. Everyone gets to be governed by the people who couldn't get to the top of anyone's list -- their platform had some compelling elements but wasn't an overall winner.
Approval voting is for executive positions. President, Governor, Mayor. Not assemblies like councils and parliaments.
Approval voting prevents the "spoiler effect". It does not enable it. Nor is it applicable to parliamentary elections, such as the example you gave.
Lastly, your comment is just weird. Equating Hamas to a spoiler. Despite the electioneering by the PLA. The subsequent extra-legal attempt to invalidate the election results that brought Hamas to power.
I'm far from an expert on Palestinian politics, but if there's a lesson to be drawn from Hamas and The Gaza Strip, it's that Palestinian politics are messy.