This is straight up disinformation. Israeli forces have killed dozens of Palestinians in Gaza since the ceasefire went into effect and continue to restrict aid from entering. If Hamas had broken the ceasefire by killing a single Israeli, just imagine how Israel would react.
Israel has actually kept the ceasefire deal and evacuated from the Netzarim corridor, a huge deal. Given the condition of the last batch of released hostages, seems possible Hamas trying to delay the next release to improve the appearance/condition of the next ones coming out.