When Alex placed the spirits into the sword, he noticed a rejection from it. It wasn't a full rejection, as the sword somewhat recognized the spirits that came from it. But it also didn't recognize them enough to fully accept them.
Alex narrowed his eyes for a second, realizing what the issue was. This was perhaps the most obvious of all the problems he had faced during the making of this sword.
And similarly, he also believed this to have the best solution of all of them.
The state his two swords had been in at the start was not the same state they had ended up in. More than that, they had been thoroughly cleansed by the purest Yang one could find anywhere in any world. Because of that, their state had changed far too much compared to what the spirits had been.
Because of this very reason, the sword did not fully recognize the spirits enough to take them in without any hesitation.
