At a guess, they are talking about Globular Clusters, not open clusters.
Globulars form around a black hole, and, some things that we call Globulars (like Omega Centaurus) are actually dwarf galaxies.
Open clusters are the residue of a nebula like the Orion Nebula. Once enough stars light up, the extra gas is swept away. But the stars remain.
I don’t think we can observe for long enough to get an answer.