It was already the plan to skip the Belgian NC TT this year before his crashes at Itzulia.I think there is some lack of confidence, after his crash in the Belgian TT last year and after his crash in the Basque Country TT. Then we are not talking about the heavy crash itself, a few days later, although not on a time trial bike. Evenepoel and his entourage also assess the risk and want to minimize the chance of another crash (in a TT). I am also convinced that Evenepoel will not be on his time trial bike much in the next two months. All attention will be paid to physical preparedness and rebuilding confidence and skills on a regular racing bike. If Evenepoel were to get close to his best form before the start of the Tour, a few time trial training sessions would probably be added.
He's not skipping it because of a lack of confidence, he's skipping it because it doesn't fit in his altitude camp plan.