I can confirm Xilibrius's observation.
I started a new build, selected Arachnos Soldier as the AT, and picked Shatter Armor from Mace Mastery. The only IO sets it will let me pick from are ToHit Buffs.
Checking in the database, the Power Name is showing Focused_Accuracy (display name is Shatter Armor). The description text appears to match what it should be for Shatter Armor. Invention Set Types is showing only ToHit IOs.
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One other observation that should probably have its own thread: In the IO Set Types tab in the power editor, I don't see the Accurate Defense Debuff icon in the group of sets that can picked from.