^^^Yes, it is true.
Getting an appraisal for a mortgage is completely different from getting a property tax reduction type appraisal.
Each appraisal is ordered by the intended user and has a specific use/purpose: which must be disclosed not only to the appraiser, but in the appraisal.
In addition to that, not all appraisers have the skill and ability to write up an appraisal for tax reduction purposes. Plus the appraiser you engage may need to go in front of a tax board to defend his or her appraisal. Find out what the full procedure is in your county/city for property tax reductions. You may want to ask appraisers how the process works generally too - and then specifically for your area. Visit appaisersforum.com in the Ask An Appraiser section to get a more knowledgeable answer to your question. I just gave you the broad strokes - there is more you should know directly from appraisers.
