If we go by this explanation then the story of Burnham hunting down the black boxes was pointless, like the music. If it was just a really loud subspace noise, on a specific frequency, then every single wide spectrum subspace receiver should have detected the Burn. That would mean all surviving installations and ships would know what caused the Burn, and the mystery would be what caused the subspace signal. It also means every surviving directional receiver would have a bearing on the source, and only two recordings would be needed to create a triangulation to nail the distance, assuming those receivers know their own positions.
That would lead to everyone knowing the source of the Burn just after it happens, and the source would have been investigated long before Burnham's arrival. That doesn't even get into the issue of how the resonance frequency of dilithium should be a known factor, and possibly something everyone already defended against.
This could have worked if Burnham had arrived just after the Burn. Then it could have been a case of the Discovery having the only safe and fast engine ready to go. Of course that would also flip the entire story line to the Federation falling apart, instead of a chance to rebuild it, and going dark was a major complaint about season 1.
As for the mutation I may be lost on that.
This sounds like she is saying Su'kal did not experience any mutations, and only gene expression increased. Doesn't that mean Kelpian's have a gene for resonating on the frequency of dilithium in response to over exposure to dilithium?