The difference is that you don't really care about the economic damage as long as it gives you the illusion that it will, by some miracle, make a difference to the numbers of immigrants we take in. It's been pointed out on here several times that any employer willing to exploit migrant workers will simply use non EU migrants. We have always had control over the number of these, but choose to import more non EU immigrants than ever. We're already showing this pattern, with the downturn in EU immigrants in 2018 being matched by an increase in non EU migrants:
https://news.sky.com/story/non-eu-mi...slows-11566853
So we're risking, if the new PM's bluff doesn't pay off (which my guess is it won't) severe economic damage for an end that will disappoint you enormously.