: I don't know how plausible or possible this "phasing" is, if it can
: even happen (I'm leaning towards no). I do know "hard light"
: itself is very far-fetched though, so any way you slice it's ridiculous.

Okay, *PRIMORDIUM SPOILERS*

There is a "scene" in Primordium in which a Halo is on collision course with a planet just slightly so smaller than its diameter. Crazy stuff goes on that involves placing Chakas in charge of maneuvering the Halo, with all the knowledge Bornstellar (as Didact) has about it.

Anyway, they decide to pass the planet through the Halo. To avoid damage due to gravitational stresses, they employ a phasing out of the compromised sections. In essence, said section were transported to a dimension (a Slipspace of sorts) in which no further action from our dimension affects them. As such, if avoids the increase in gravitational stress while maintaining the inertia.

It is not a complete Deus Ex Machina because it takes a lot of energy, almost all the energy this particular Halo can afford.

Also, apparently, it is not dissimilar to the timelock that was applied on the Captive of Charum Hakkor, so it would explain why it took so long for the Chief to be surrounded by debris, while also explaining how they had so much time before the hard-light wall collapsed.