Archon skills cancel itself out after using a melee skill, is this a bug or it's by design?

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Archon Buff
Archons are a type of Buff that augment your Elemental prowess with Spells. There are Archon Buffs related to each Element: Flame Archon, Ice Archon, and Lightning Archon.

By default each Archon Buff lasts 10 seconds, but will be removed early if you use any non-instant Attack.

You cannot gain any Archon Buff while you already have one, or during a recovery period after you lose one, which lasts 20 seconds by default.