A particle needs a stable identity. Mass needs a meaningful response to motion and deformation. Energy needs comparisons that make transport, change and conservation meaningful.
When the outside support is lost, these are no longer fully secured physical roles. Recognisable field patterns, particle-like organisation and source-like behaviour may remain, but they are no longer ordinary matter and energy with their former standing.
This is the sense of degeneracy here: remaining structure without the full support that made its former physical meaning possible. It is not a claim that matter suddenly vanishes at the horizon.
What changes when the support is lost?
MatterRemaining patterns, without fully secured particle identity and physical roles.
EnergyRemaining source-like behaviour, without the former basis for its energy accounting.
Not ordinary continuation. Not simple nothingness.