Their explanation of the background subtraction methodology seems pretty clear to me, and I don't see how their statement in the first paper could be construed as misleading nonetheless deceitful.
They are able to show how they went from the raw data to the published. Unless you are claiming that the raw data itself is completely made up (in which case why not just make up data that gives the result they want with a different background subtraction method?) then I don't see how the validity of the raw data is in question.
"We selected the background after carefully investigating the temperature dependence of the non-superconducting CSH sample at 108 GPa, the closest pressure prior to the superconducting transition. We note here that we did not use the measured voltage values of 108 GPa as the background. We use the temperature dependence of the measured voltage above and below the Tc of each pressure measurement and scale to determine a user defined background (Fig. 2a). The scaling is such that one achieves an approximately zero signal above the transition temperature; the subtracted background isolates the signal due to the sample."
I challenge you to actually repeat what they did using that description. It is not a complete description.
And no, they did not "show how they went from the raw data to the published". Just because they said they did, doesn't mean they did.
The raw data is in question because it's impossible to understand how subtracting two noisy data sets would produce data that is a combination of a spline and digitized data.
They are able to show how they went from the raw data to the published. Unless you are claiming that the raw data itself is completely made up (in which case why not just make up data that gives the result they want with a different background subtraction method?) then I don't see how the validity of the raw data is in question.