But the warrant still has to originally exist with, presumably, a timestamp that shows it existed prior to the search. And modification of the timestamp or lack of such a feature would be a good way to get the evidence thrown out?
The existence of a category of warrants that allows operation that is indistinguishable from warrantless searches creates a kind of legal hazard and personal risk that is hard to overlook. Police lie on the regular.
I don't get why people downvoted you, this is a very reasonable question.
That’s not how evidence works in Canada. Illegally obtained evidence is still evidence - you simply also have a tort against the officer for breaching your rights.