Okay, let's see...
I understand this is an "accounting move" for Juventus, I understand that!
The relevant questions here is...
What makes us think that any team would agree to take a player on loan who hasn't played in a year... a player whose injury isn't clear yet!
I understand this type of move when we're talking about players who earn a lot of money and who you can't sell for that reason, like Arthur...
Milik's case is different. We're talking about a player whose return from his injury, when he'll return from his injury, and if he'll even return from his injury its still in the air...
Wouldn't it have been better to sit down and talk with Milik and say,
"Listen, You've been injured for a year. We've paid you your full salary for the year you were injured. We've been patient with you, we've been good to you. You have one year left on your contract. Let's negotiate a termination, and you can look for a team as a free agent."
If Milik agreed to distribute his salary, if Milik agreed not to receive part of his salary this year, it's entirely plausible that he would have agreed to terminate his contract and, at most, ask for a minimum amount to do so...