And has it been demonstrated that every single cave dude took it so seriously that in every single case they always buried dead dudes the exact same way?
No, of course not.
This conclusion that these "scientists" are making would be an example of the logic fallacy of Reverse Fallacy of Accident
Or if you want to be a pompous jerk like me:
a dicto secundum quid ad dictum simpliciter 
Simply because "A" has been observed across a wide sample, does not mean that all or any future samples will reveal "A". This is why polls can only serve as general indicators.
So unless these "scientists" can demonstrate that a group of dead guys were all buried by the same group of diggers, at the same time, under the same circumstances AND this was the only one what was buried differently, their conclusion is not supported.
Boy I can just imagine my trying to get this stuff past my Dissertation committee. My Chair would have my guts for garters.
