  The multi-messenger observations of the merger event in GW170817 did not rule
out the possibility that the remnant might be a dynamically stable neutron star
with $\mathcal{M}_{rm}\geq 2.69 \,\mathcal{M}_{\odot}.$ Based on this and other
recent events, I argue that the universal maximum density hypothesis should be
revived. Accordingly, the central densities in the cores of ultra-compact
objects must be upper-limited by the critical density number $n_{cr},$ beyond
which supradense nuclear matter becomes purely incompressible.
  Based on the spacetime-matter coupling in GR, it is shown that the topology
of spacetime embedding incompressible quantum fluids with $n =n_{cr}$ must be
Minkowski flat, which implies that spacetime at the background of ultra-compact
objects should be of bimetric type.
