Scanning Helium Microscopy (SHeM) measures scattered helium intensity from a spot on a surface; conventionally, the interesting content in images comes from the contrast between pixels that has various origins. In the review, apparent observations of chemical contrast in SHeM are considered, particularly the potential for a link with theoretical treatments of inelastic scattering, particularly using the Debye-Waller Factor (DWF). The on-specular reflection form of the DWF cannot be directly applied by itself, but rather, an energy integrated differential reflection coefficient- which includes the DWF and scattering distribution in the scattering transition rate- would be the appropriate measurable for the SHeM. The literature shows that formalisms for the DWF and scattering transition rates would be expected to produce material dependent or chemical contrast; however, expressions for a general inelastic transition rate for helium is intractable. The assumptions of the Debye-Waller formalisms suggest that they would not be able to explain the apparent chemical contrast observed. Therefore it will remain to be seen whether the DWF formalism will lead to an improvement in the ray-tracing comparisons to data. Chemical contrast would make a significant impact on the applicability of the SHeM technique, especially if it could be understood and predicted for chemical imaging; the Debye-Waller mechanism may play a key role in understanding and probing 2D superconductors.