The breaking of the conserved number of cervical vertebrae is hard to reconcile with an unguided evolutionary mechanism.
There is a long-running about whether birds first took off by running and flapping from the ground up, or whether they jumped as gliders from the tree down.
This is not how good science is supposed to work but is rather typical for pseudoscience that shields itself against empirical falsification.
I could not find a single reviewer who accepted the claims of the papers. They were harshly critical of claims of intentional burial of the skeletons.
Remarkably, these animals can be placed within the crown group of the living cnidarian clade Medusozoa, which is not exactly what Darwinists should expect.