If this was so widely supported by the community, there would be an actual paper that used this equation to calculate atmospheric heat content anomalies surely? (realclimate.org)
There is nowhere in that paper, or any other, that relies on some assumption about atmospheric heat content anomalies. (realclimate.org)
But your papers claim of a «bias» in the surface temperature record * if * it is used as a linear predictor of atmospheric heat content only makes sense * if * indeed people had used it in that sense. (realclimate.org)