No the proximity fuse or airburst, like you say, goes back to WW2. Shell blows up above ground and the outside case as well as internal shrapnel is distributed by the shell explosion.
The cluster munitions, the internal bomblets in the shell have their own separate explosives, and they can land and explode later.
ARTICLE
Sky News [excerpt]
Friday 7 July 2023 23:21
https://news.sky.com/story/ukraine-war-latest-russia-putin-wagner-prigozhin-belarus-12541713
“It is ‘intolerable’ that Ukraine be allowed to run out of artillery.” Jake Sullivan, National Security adviser, defends sending cluster munitions to Ukraine, saying they will be sending a version that has a REDUCED “dud rate”, meaning fewer of the smaller bomblets fail to explode.
The unexploded rounds, which often litter battlefields and populated civilian areas, cause unintended deaths.
“We recognize the cluster munitions create a risk of civilian harm from unexploded ordnance,” the National Security adviser said.
“This is why we’ve deferred the decision for as long as we could.
“But there is also a massive risk of civilian harm if Russian troops and tanks roll over Ukrainian positions and take more Ukrainian territory and subjugate more Ukrainian civilians, because Ukraine does not have enough artillery.
“That is intolerable to us.”
Russia spent months digging into defensive positions, surrounding them with landmines and building heavily armed fortifications making Ukrainian advances in the east and south slow and bloody. Russia had been indiscriminate in their use of cluster munitions with a much higher risk of collateral damage. Russia has been using cluster munitions since the start of the war.
“The munitions we will provide Ukraine will have a dud rate of below 2.35%. And, we are working with Ukraine to reduce the risks associated with these weapons.” Ukrainians would be reporting back the usage of these weapons to the US.