There is nothing inherently wrong with an appraiser providing a value opinion. That is why we are hired

The complication arises from the fact that the 1004 is labeled as an Appraisal Report, not a Restricted Report. That means that support must be provided for appraisal opinions reported in that format. See Sr 2-2(a)(viii).
So, for example, if one says that a prior sale was at below market value, then one has communicated an appraisal opinion via reference to a benchmark, and then one takes on the obligation of providing a summary of the analysis and data that supports that (retrospective) value opinion.
It is not the communication of a value opinion that is the issue. Rather, the issue is that in most (nearly all) such cases the statement is presented without the required supporting commentary.