I believe the argument is that event horizons exist but inside is not a singularity, but an eternally collapsing mass of the original star. From the point of view of the star, it does collapse all the way, but from our point of view that final singularity collapse is in the indefinite future.
Update: I am mistaken. The classic GR black hole behaves this way. MECOs supposedly never fully collapse into a singularity, even for infalling observers. That's the difference.
I rather think we'd have noticed the difference from LIGO gravitational wave measurements of BH mergers, but maybe not?
https://en.m.wikipedia.org/wiki/Magnetospheric_eternally_col...