My question is pretty simple. Having a valid igc trace file, do I need
an OO for a duration claim ?

Yes, there is no trust in this business. An OO has to certify that the
trace is yours and that it is valid and has not been tampered with. The
OO has to sign about three or four different statements. It is always
about the paper work more than about the flying.

This condition exists, sadly, because some people were caught cheating.
A pilot was stripped of all his badges, dismissed from membership in
SSA, and the numbers for his badges stand today as empty ciphers in the
list of badge holders.

Nyal Williams