This is terrible, it takes a lot of attractiveness out of AS miles as I was planning to use a lot of AS miles for just this purpose.
Place not your faith in princes or in fiat pseudo-currencies that you don't even own.
Awards or accrued Miles, including purchased Miles, do not constitute the property of the member to whose Mileage Plan account the Miles have been posted. However, awards or accrued Miles do provide the member with an option to exchange such Miles for travel at the redemption level in effect at the time of redemption (not at the time of accrual).