All old epic items with spell power got that update around U14, just non retroactively.
More of a side effect rather then the devs actually changing anything, they just default to standard funtionality of spell power items after the cleansing. (ml20 = 90).
If you could change their min lvl, the power would likely go up. Though theres no way to do that atm (new augments could add ml24, but it adds it as absolute ML, which doesnt actually change the ml which the spell power is based on).