Edited Oct 14 at 3:13
I believe that conditioning assignments can only last a certain period of time (two weeks I want to say?) and there has to be some kind of injury to the player for it to take place. Dach was injured during training camp, so he qualifies for this assignment. It kind of is a loophole, and it can work to the Blackhawks' advantage, as it gives them a look at how Dach performs at a higher level of competition than he would see in the WHL. But then again, it's not like they can keep him down there all season.
Not really the same situation, but I do know that players that require waivers can actually bypass waivers when they're sent to the AHL on conditioning assignments. So there are some loopholes when it comes to this rule, but there are some safeguards to prevent abuse of it.
Edit: Here's the rule (13.8) from the CBA:
Conditioning Loan. Unless a Player consents, he shall not be Loaned on a Conditioning
Loan to a minor league club. Such Conditioning Loan shall not extend for more than fourteen
(14) consecutive days. The Commissioner may take whatever steps he deems necessary to
investigate the circumstances under which a Player is Loaned on a Conditioning Loan. If the
Commissioner has reason to believe or determines that the Club has used the Conditioning Loan
to evade Waivers, or otherwise Circumvent any provision of this Agreement, he may take such
disciplinary action against the Club, as he deems appropriate. The Player shall continue, during
the period of such Conditioning Loan, to receive the same Paragraph 1 NHL Salary, and be
entitled to the same benefits, that he would have received had he continued to play with the Club.