I've used a Maasdam rope puller for 25 years and never had a rope slip problem. From the visuals in that video, he wasn't using the right rope and I'll bet he bought just the puller and was using a non-recommended rope. Those pullers require three strand. That carabiner also looked dodgy. Maasdams should come with a load rated hook on each end.
A rope puller won't land your tree on a dime if you don't make a proper hinge. It will help with back lean and pulling a limb bound tree loose, but once the tree is on its way down and the line goes slack, that tree will go where your hinge aimed it. Also keep in mind that a single rig will start the tree towards you. An offset block on your aim tree to redirect the rope to an anchor tree for the Maasdam is a safer approach.
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