Smerel, that account by r. Lorencz is a mistake. The satmar rov didn’t say that nissim are from the soton, he said that there weren’t nissim in the 6 day war, and he was correct. The US military said it would take Israel around a week to do what it had to do.
And yes, attributing anything to the independent acts of the soton, or anything other than Hashem, is kefirah.
But the brisker rov wasn’t arguing on tje established concept of maysoh soton whch is mentioned in chazal(one place that comes to mind is the image of Moshe dying on har sinai before the egel). What it means is that the soton is doing his job that he was tasked to do by Hashem and is only able to do so because Hashem wants that test to be made.
That’s why it says in chumash that when a navi sheker does a miracle, it’s Hashem testing you – He is testing us through the soton to see if we will go with the sitra achra.