I am going to chime in knowing very little about the player but just looking at the lads stats and I will break them down to add something to the debate.
Ajax (1 Season)
13 Goals, 6 Assists, 3074 minutes which works out to 34 full games. That is 19 goal contributions in 34 games.
Lyon (All Seasons)
33 Goals, 17 Assists, 7649 minutes which works out to 85 full games. That is 50 goal contributions in 85 games.
Lyon (Last season but included in the above stats)
4 Goals, 5 Assists, 1913 minutes which works out to 21 full games. That is a 9 goal contribution in 21 games.
So that is the raw unarguable data on Bertrand Traore, I put in last seasons stats because people said he was so terrible.
My conclusion based on his goal contributions is he should be a good signing.