FASB - IAS convergence

An Accountancy Age article reports the recent fair value proposal by the FASB:

The FASB today moved a step further along its IFRS convergence journey with a proposal that would allow companies the option of reporting financial assets and liabilities at fair value.

The article goes on to provide this information:

The FASB added that the change would simplify accounting and reduce earnings volatility caused by differences in current accounting rules.

If implemented, the new standard will allow financial assets and liabilities to be measured at fair value on a contract-by-contract basis. Companies will have to display these values separately from those measured under different attributes on the balance sheet.

I wonder how having an accounting fully based on market value principles would lead to reduced earnings volatility? It would seem to me that mark to market accounting would only lead to more volatility as the changes in interest rates, market values etc. would create a lot of variability.