This mechanism means that regardless of how awful the Trump admin proposal one SCOTUS justice can "temporarily" unblock it giving no reason at all, and then the "real" merits case can be slow-walked.

Slow-walked, conveniently, until the admin has finished doing whatever the original lawsuit claimed was illegal, and then the government argues it is impossible to undo after the fact.

The problem is that the rationale is hidden, not that criticism of it is hidden. If the Supreme Court doesn't explain why they make momentous, weighty decisions, that leaves the rest of us with only speculation, both in understanding how the decision should be applied to other cases and evaluating whether the decision made any sense at all.

(I agree that there's nothing fundamentally wrong with the even more recent trend of shadow docket decisions that do come with opinions attached, and perhaps law students in the 2030s will learn about the "expedited docket" as a normal way to handle cases.)