And yet if you want to know how a monster's skills work... you reference the PHB. How it's spells work... reference the PHB. How to make an attack roll for a monster...reference the PHB. Thus I'm not sure your assertion holds up. I would say they are two interdependent books...
Unpon reflection, yeah, I'm gonna have to agree with you here. Good point.
Well first the monster can in fact use general actions like grappling, shove, dash, etc that are available to all creatures... This is stated in the Monster Manual under Actions. The main point of contention is whether it can sacrifice one of it's attacks in multiattack to do so.
No, for the simple reason that "Multiattack" is
a single Action choice. It is not "a bunch of actions slapped together under this word for no particular reason". I mean, looking at, say, a dragon...would you accept that it could us "Multiattack" to use Claw, Claw and the Breath Weapon? I mean, all it's doing is 'substituting' Breath Weapon attack for it's Bite attack under the "Multiattack", right? Why can't it do that if you let it get away with Claw, Claw, Dash? Breath Weapon is an Action choice of its....just as Dash would be.
That is why 'subbing' some other Action with a Multiattack attack makes no sense.
IMO, there's no point to allowing all creatures to take certain actions if they are always a suboptimal choice... in other words if I have multiple attacks and have to sacrifice all of them in order to grapple or shove... I'll probably never use any of those maneuvers with a monster... the cost is just way too high.
Gawds I hate that term..."subotpimal choice". Its the same thing as saying "Anyone who chooses to have a white care is an idiot because white cars are the most common color of cars that get into injury causing accidents"; some people really like white...their "choice" isn't "suboptimal" except in
that one, single VERY narrow view of car safety. It's a choice. Choosing to Grapple with the spellcaster may be the best choice in many situations...just because it doesn't actually inflict DPS does
not mean it is "suboptimal".
Okay so here's a question... if a monster/npc can only ever use it's stated weapons for multiattack... how do the rules for armor and weapon swaps for NPC's interact with this? If you give them different weapons can they say use multiattack with those weapons even if it states specific weapons for it's use in the stat block ... or can they use the new weapons you've given them with their ability even if it's not implicitly stated?
Sure they can...
MM, p6, Modifying Creatures: "... Feel free to tweak an existing creature to make it into something more useful for you, ...".
Regardless of that little side-bar in the MM, it goes without saying, really, that a DM can/should modify whatever he feels is best for his campaign. So, as I said at the end of my last post, a DM should do what he feels is cool; if swapping out other attack-choices with Multiattack is cool for you, do it. If it's too open ended, pick a few select combat actions (Grapple, Push, Dash, Dodge) and only those can be swapped. Or, just say no and make it Multiattack as is, -or- a different Combat Action.
At the end of the day, its your game. But, by my reading of the rules and what makes sense from my perspective....no, a monster can't swap-out one of it's claw attacks to perform a Dash any more than it could swap out a Claw attack and perform a Breath Weapon attack.
^_^
Paul L. Ming