The "beautiful" thing about perfidy is that it's a particularly well defined war crime and it's relatively easy to prove in the era of cameras everywhere.
What isn't permitted is fighting in civilian clothes, but if you read the article, there is nothing indicating that they did. It is entirely legal to move about and set up an attack in civilian clothes, provided they are discarded immediately before striking.
Eyewitnesses tell Asharq that beside the disguised troops, other special forces snuck into the Nuseirat camp inside an aid truck. The IDF has denied using humanitarian transports for the operation.
From the link you posted, it seems this would still be a war crime if it's true, unless I'm misinterpreting the text:
Ruses of war are permitted. Warships and auxiliary vessels, however, are prohibited from launching an attack whilst flying a false flag and at all times from actively simulating the status of protected vessels such as hospitals ships, small coastal rescue craft or medical transports.
I assume the aid truck they were using would qualify as an "auxiliary vessel", and they were using it to impersonate "medical transport".
Note also:
The rescue unfolded under intense fire, and during the withdrawal, dozens of terrorists armed with anti-tank missiles and machine guns surged through the alleys toward the targets. As a result, uninvolved Gazan civilians were also killed in the densely populated area.