The 2.5% is a number they pulled out of their ass. The real number is close to 10-15% (these are not new munitions, they were manufactured in the 80s and the numbers come from tests back then).

Even if 2.5% is true, each bomb carries around 200 bomblets. So for every bomb used, 5 bomblets will remain unexploded until someone stumbles upon it. The bomblets are also small, spherical and usually painted bright green or yellow. Kids who found them before, and survived, reported they thought they were tennis balls and used them to play.

Furthermore, there's a law in the US that prohibits exporting cluster munitions with more than 1% dud rate. Of course, Biden has said they'll just bypass that law. Meaning this is illegal both internationally and nationally for the US.

Finally, the US is saying that Ukrainians assured them they would not use them "irresponsibly". However 14000 Donbass, Donyetsk and Crimea residents would tend to disagree if they were still alive today.

(edit: and even if the Ukrainians try to use them "responsibly, these munitions are highly innacurate by nature and Ukraine does not have and will not have the logistical capacity to clear out duds/