Statement of competency of will testator

In the last will and testament of an elderly person who currently resides in a nursing home, how important is it to include a statement of the testator's competency? If the individual (testator) is competent, and the attorney drafting the will refuses to execute the will -- and, consequently, intentionally excludes a statement affirming the testator's competency from the will since he is not personally meeting the testator, would a written testimony (affidavit) from a physician and/or psychiatrist who knows the testator over a long period of time be legally acceptable proof of the testator's competency and thereby legally enable to attorney to include a paragraph affirming the testator's competency in the will? Thank you for your anticipated response.

To avoid a dispute later it is a very good idea to have reputable medical staff or experts confirm competency.