i can find multiple sources for the losses to: Gaydarbekov, Hikal, Austin, Dirrell and Gutknecht but not for Galochkin, Despaigne or Prasathinpimai, the latter loss supposedly being at a muay thai event.
that pretty much confirms at least 6 losses then. apparently someone has embellished his record, at least to some degree.
ya, it wouldn't surprise me if many adopt that attitude but we know todays Triple G would knock his amateur self out in a round or two with ease.
For Olympic test event, I'd suggest searching for the Acropolis Cup, it was won by Dirrell... Who beat Despaigne I'm the final. Can't find many links but I'm using an old ****py phone at the moment
Strefa has had this partial record for several years with occasional updates (one?). They have a few others, mostly of the very good amateurs, but mostly they archive competition records and that's probably enough work to not really bother with individual records. Anyway, amateur boxing is about what you win, imo, not the number of losses.