Does Skyfall of Areion make Yone Blademaster ability trigger on holds?

No, Skyfall of Areion does not cause Yone, Blademaster's ability to trigger on every "Hold" action.

1. Skyfall of Areion's Function

According to FAQ #5622 and #288, Skyfall of Areion modifies the equipped unit's triggered abilities, allowing "When I conquer..." effects to trigger on both Conquer and Hold scoring, and "When I hold..." effects to trigger on both. It only modifies the equipped unit's abilities and does not change the fundamental definitions of the "Hold" or "Conquer" actions, nor does it override the specific conditions (such as "uncontrolled") within a unit's ability text.

2. Yone, Blademaster's Condition

Yone, Blademaster’s ability requires: "When I conquer a battlefield that was uncontrolled..." A standard Hold action is defined as maintaining control of a battlefield you already control (Rule 464.2). Because you already control the battlefield during a standard Hold, the condition that the battlefield was "uncontrolled" immediately prior to the action cannot be met. Consequently, Skyfall alone does not satisfy Yone's "uncontrolled" requirement.

3. The Exception: Reckoner's Arena

The confusion regarding this interaction stems from specific FAQs (#9342, #9002) involving Reckoner's Arena.

• Reckoner's Arena has the unique ability: "When you hold here, activate the conquer effects of units here."
• This battlefield effect acts as a bridge: it forces the "When I conquer" abilities of units present to trigger during a "Hold" action.
• It is this unique battlefield ability that creates the window where Yone’s ability can trigger during a Hold. Even then, the "uncontrolled" condition must still be satisfied.

Summary

• Does Skyfall make Yone trigger on all Holds? No.
• Does Skyfall make Yone trigger on all Conquers? Yes, because Yone is a conquer-based effect and Skyfall enables that.
• When does Yone trigger on a Hold? Only when an external game effect (like Reckoner's Arena) specifically forces a "Conquer" trigger to fire during a "Hold" action, and the specific condition of that unit's ability (e.g., "uncontrolled") is independently met.

Note: I could not fully verify the interaction between the 'uncontrolled' condition and the Hold action against the retrieved rules.