The temporal qualifier is inherent in the grammar of the statement. Perhaps you didn’t notice it?
In English, the present perfect continuous has/hasn’t been taking implies a frequent and repeated action since a fixed time in the past - in this case, presumably, the start of the current conflict until now.
Since Hamas only took civilian hostages on one occasion, i.e. October 7th, and not again since, it is not true to say that Hamas “has been taking hostages”. They took hostages. Once.
Israel, on the other hand, have been taking Palestinian civilians captive, repeatedly, since October 7th. That’s the difference.