Not just learnt today but proof that supports what I knew -
Gates wrote an article that was published in a Hot Rod magazine about how Subarus, due to their design require extra consideration and care taken with their timing belts and tensioner as any friction due to an incorrect fitment causes heat transfer and premature failure to big end bearings.
They supply a tool with their belt kit which sets the tensioner gap correctly, also noting the torque settings
Surprise surprise huh. I guess it comes down to whether you trust your mechanic