I'm just out of this discussion. I can already see where this is going.
This is fair. I just gave my reading of the rule. I'm not particularly passionate about arguing in favor of it.
EDIT: Not much content in that post, so I would like to respond to a thoughtful post by SagaTympana to explain my thinking on the matter. Obviously, I'm not an authority and this is more of a logic exercise than arguing that my position is explicitly supported by the rules (spoiler: it isn't)
My response is that if "the casting time still applies," Molydeus can't cast a spell with a casting time of one Action either, because Molydeus doesn't have an Action to cast it with. The cast a spell action does not substitute for a spell's casting time; it's not an "action" in the sense that it takes your Action; it takes whatever time the spell's cast time is. If the cast time is one Action, then casting the spell requires an Action. Legendary Actions do not give creatures any extra Actions the way Action Surge does. If Legendary Actions can't be used to cast one minute spells, they can't be used to cast one action spells either.
This is a really good point. But I'm not sure it matters in terms of the position I'm taking. Any spell that has a casting time of any action (action, bonus action, reaction) goes off at the time the spell is cast. That puts all of those spells into one category and leaves a second category of any spells with casting times longer than any action because they have to "build up" before they go off. The distinction I'm drawing with a legendary action isn't that I think it's a special kind of action, but that the thing that makes it legendary is that you are able to use it out of turn. When I refer to the cast a spell action, all I mean is the procedure of casting the spell. You say, "The cast a spell action does not substitute for a spell's casting time," and I agree with this. My position is that the spell itself informs how long it takes to go off.
This is fair. I just gave my reading of the rule. I'm not particularly passionate about arguing in favor of it.
EDIT: Not much content in that post, so I would like to respond to a thoughtful post by SagaTympana to explain my thinking on the matter. Obviously, I'm not an authority and this is more of a logic exercise than arguing that my position is explicitly supported by the rules (spoiler: it isn't)
This is a really good point. But I'm not sure it matters in terms of the position I'm taking. Any spell that has a casting time of any action (action, bonus action, reaction) goes off at the time the spell is cast. That puts all of those spells into one category and leaves a second category of any spells with casting times longer than any action because they have to "build up" before they go off. The distinction I'm drawing with a legendary action isn't that I think it's a special kind of action, but that the thing that makes it legendary is that you are able to use it out of turn. When I refer to the cast a spell action, all I mean is the procedure of casting the spell. You say, "The cast a spell action does not substitute for a spell's casting time," and I agree with this. My position is that the spell itself informs how long it takes to go off.
"Not all those who wander are lost"