I'd say that to call his puppeteering "unholy life" to "dead guardians" would imply the guardians are alive to begin with.
What could have happened is the Hylians hit the "kill" switch on the Guardians when they were hijacked, but to no avail until Ganon's malice was driven out.
For that matter, my (stolen) pet theory is currently still that the blights are a similar type of malice possessing the armor of the original champions.
Plus Ganon has demonstrated assimilation of ancient tech and Robbie hasn't been able to figure out how to repair guardians, even perfectly functional ones he took out himself.
I'm saying there's a fundamental difference between normal, functional Guardians and the ones Ganon is controlling besides that they're just berserk. It's not a big difference, but it's enough that i don't think Ganon-controlled guardians can be repaired, even if Ganon is purged. They'd have to be rebuilt or something.