I guess you are right if the discussion was truly about Trump's personal tax return exclusively - although concerns about family are still relevant.   The fact that Politifact said it was a personal return is not compelling.  The fact that Trump mentioned that others' concerns might be involved suggests to me that Trump did not mean simply his personal concern.

The bottom line here is that Politifact did not set out the precise assumptions used in making a false determination.  Among the key assumptions is that the return is purely personal.  Trump did not say that in his statement.  I saw no discussion of how Politifact determined precisely what type of return was under discussion.  Also, it should be noted that Trump as CEO of an S corp would have an fiduciary obligation to minimize taxes the corp paid directly (if any).  In total, a complex situation in which a conclusive false is not helpful to anyone and appears purely politically motivated.