It mentions that claim but now there is no evidence provided of it either, yet.
More interesting to me is the news that it wasn't the extraction that created casualties, it was the group somehow getting stuck and the militant counterattack that spurred escalation. While I do not condone the Israeli attitude towards casualties, I don't condone the Hamas attitude towards them either.
Presumably they factored Hamas not willingly handing over the hostages into their planning. If their contingency plan for meeting resistance was just to bomb areas full of civilians until they could get out, it still shows a lack of regard for Palestinian lives.
Hamas sacrificed some number of militants and innocent people that add up to 274. All were not innocent unless you think these hostages were on a impromptu vacation.