Let's break this down, as far as we know the only way to get a neutron star is when the core of a very massive star collapses when it dies. The inner core is crushed to super high density electron degeneracy conditions (white dwarf star matter) and then a core of that matter builds up that is too heavy to resist further collapse, and then a neutron star forms. This would naturally lead to a minimum mass for neutron stars, at about 1.44 solar masses, which seems to be born out by observations, so far. This object appears to be a neutron star density but only 0.7 solar masses, which would put it more in the realm of what should just be a white dwarf.

One other issue is that neutron star material is not necessarily stable under less pressure, and would simply decay into atomic matter.

This raises the question of how this object got from point A (the core of some dying star, most likely) to B (a sub-stellar mass neutron star), and there are lots of possibilities. The possibility being floated here is that the object is not a neutron star per se but rather a "quark star" or a "strange star" where instead of being made up of mostly neutrons it's actually made up of an arrangement of quarks with a mixture of strange quarks in a configuration that allows it to be stable in that mass range. It's been proposed that it may be possible for "strange quark matter" to exist in forms which would basically catalyze the conversion of neutron star material into it at similar densities to neutron stars. It may be that this is an example of a fragment of a neutron star that underwent a conversion to a quark star and then lost some of its mass in some way, or it might be a more direct conversion of a white dwarf into a quark star. There are a zillion questions still to be answered and this is an intriguing piece of evidence, assuming it holds up to scrutiny.