Voldemort believes himself to be basically immortal at this point, so he can get away with taking some riskier decisions than he might otherwise. Worst case scenario he has to go embed himself in somebody else’s head and start over. Presumably he can blow up his body or something if necessary.
Harry doing the memory erasure only happens because of the specific combination of information and abilities Harry had.
Reminds me of something about trauma being adaptive responses to a particular situation that are no longer adaptive in the current situation. E.g. being hyper vigilant is useful in genuinely highly dangerous environments but not elsewhere