I don’t know what you mean by an SYG continuum. I’m not familiar with “SYG.”
Regardless, I think it is unrealistic, and probably unreasonable, to expect a civilian to adhere to a “continuum of force” when his head is being slammed against the concrete and his nose is being violently smashed.
I don’t think a policeman would restrain his force under the same circumstances, either.
SYG = stand your ground
The continuum of force model might be better recognized as escalation of force principle: a police officer may only select the minimum amount of force necessary to control a situation. As a guideline, in an incident between a police officer and a suspect, if the suspect uses some kind of force to resist control, the officer may only proceed one step higher in the force continuum to achieve control.