Yes, it's more to do with the material the xray tests are recorded on. Probably there are other medical tests that are recorded on film too, but 'medical film' is not a term the average person would hear often, if at all. Different terminology is used when you are looking at the results. While an xray or other tests may be recorded on film, normally the term 'image' is used when discussing the results viewed on this film. ct scans and mri results will use the term 'scan' or 'image' when results are discussed.

Note that X-Rays are usually done digitally these days. Films are probably a thing of the past in most places.