TurboTax only needs to know your age at the time of the of the distribution if the distribution was a taxable distribution. Distributions that are not for payment of qualified medical expects are subject to income tax and, if you are under age 65 at the time of the distribution, to a 20% extra tax. If the distributions were not used for any qualified medical expenses you'll need to split the Form 1099-SA into two, one for the portion received before age 65 (subject to the extra tax) and the other for the portion received after age 65 (not subject to the extra tax).
If you used all of the money for qualified medical expenses, it doesn't matter what answer you give since nontaxable distributions are not subject to a 20% extra tax.