At the moment Danny Olmo is still not registered and will not take part in Barcelona's first game against Valencia and I think that if Barcelona could have registered him, they would have done it already, because it is unlikely that Barcelona would have paid 60 million euros for him.
Although Flick says that Olmo is not fit yet, but I think it is just a formal excuse, because Olmo played his last match more than a month ago in the final of the European Championship and it is unlikely that he has not had time to recover yet.
So in other words you're saying Barcelona will loan or sell him since they won't be getting any 60 million to register Olmo? Is that it? Olmo did not take part in the friendly match against Monaco, in fact, he did not play any pre-season game so how do you expect him to play in a league match? He has only had a few training sessions with the team, that alone should let you know he is not ready. The coach, who is an insider gives an update on the situation of a player, you doubt it, but if the media says "Barcelona is too broke, they might have to loan out Olmo" you'll believe?
Mind you, the other players you mentioned Martinez, Torre, Pau Victor and Alex Valle have all been registered. If registering Olmo will be such a big problem for them there are other players in the squad that they could have sacrificed, not their new 60 million signing.