As cletus said above, black holes have only three externally-observable properties: mass, angular momentum, and charge; see for instance [1].
Note that radius/size is not one of those three. The radius of a black hole derives from its mass under general relativity, and no amount of change found in the density nor size of neutron stars will change that.
You're right that new understanding of neutron stars has implications for other things in cosmology, though.
What this changes is how much mass a neutron star can have before it collapses into a black hole. That limit is defined by when the neutron star's mass fits within the size of an equally massive black hole.
Not exactly. Certainly it is a black hole once a neutron star's mass fits within a certain radius, but since it is then not a neutron star any longer, the question is how that condition came about.
Neutron stars have an effective outward pressure that is caused by the Pauli exclusion principle [1]; two or more fermions such as neutrons cannot be in the same state (which includes location). A strong enough inward counter force from internal gravity (or from an external force) will cause a net motion inward, overcoming the outward force, such that enough matter (more accurately, enough mass-energy, not just matter) is within the critical region.
Note that radius/size is not one of those three. The radius of a black hole derives from its mass under general relativity, and no amount of change found in the density nor size of neutron stars will change that.
You're right that new understanding of neutron stars has implications for other things in cosmology, though.
[1] https://phys.org/news/2020-12-black-holes-gain-powers-fast.h...