I found the criteria list and it says the BOIC selects male tennissers ranked in the top 25 I think or they need to have reached 2 slam quarters or something like that. So I guess Olivier an Xavier just don't have accomplished what they need to to be selected.
Now I found the A-B-C lists of athletes. Olieiver and Xavier or both on the C-list. That's a list of young athletes who have provern their talent with good results. So I hope they still have a chance to be selected based on this instead of the 'real criteria'.
It's a complicated selection system!