Dragonwrath, Tarecgosa's Rest

This achievement will be awarded for crafting, and completing the exciting and legendary quest chain to obtain Dragonwrath, Tarecgosa's Rest.

Wielder of Sulfuras, Hand of Ragnaros.
Wielder of Thunderfury, Blessed Blade of the Windseeker
Wielder of Atiesh, Greatstaff of the Guardian.
Wielder of a set of Warglaives of Azzinoth.
Wielder of Thori'dal, the Stars' Fury.
Wielder of Val'anyr, Hammer of Ancient Kings.
Wielder of Shadowmourne.
Owner of Dragonwrath, Tarecgosa's Rest.

"Owner" instead of "Wielder" like the tooltip on other legendary achievements.

Lets check the corresponding guild achievements for these Legendaries, shall we?

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• Owner of Sulfuras, Hand of Ragnaros.
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• Wielder of Thunderfury, Blessed Blade of the Wind Seeker.
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• Atiesh doesn't have a guild achievement
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• Owner of a Set of Warglaives of Azzinoth.
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• Owner of Thori'dal, the Stars' Fury.
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• Owner of Val'anyr, Hammer of Ancient Kings.
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• Wielder of Shadowmourne.
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• Owner of Dragonwrath, Tarecgosa's Rest.
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I'd say it's perfectly in order to mix "owner" and "wielder" without any discernible pattern.

The questline is class locked, and the completion requirements are the last quest. The wording means nothing.