The Merfolk Salvager's melee attacks don't specify that they're "Weapon Attacks". Is there a reason for this?

Question

I noticed that both of the two attack actions a Merfolk Salvager (GoS, p.244) has do not specify that they are Weapon attacks:

Coral Rapier. Melee Attack: +4 to hit, etc.

Inject Toxin (2/Day). Melee Attack: +4 to hit, etc.

I've scoured the MM, the MToF, and some others but this seems to be a first for any monster. It's also not mentioned in the GoS Errata.

Is this a slip of the pen, or is there a reason behind it? Also, how would this affect the use of this monster?

Answer 1

According to the rules in the Monster Manual, it is just a mistake.

This particular section of a monster's stat block is described in the introduction to the Monster Manual, under "Melee and Ranged Attacks":

These can be spell attacks or weapon attacks, where the “weapon” might be a manufactured item or a natural weapon, such as a claw or tail spike.

This rule tells us attacks in monster stat blocks are either spell attacks or weapon attacks, and even natural "weapons" get labeled as "melee weapon attacks". Since these two attacks (a manufactured rapier and the venomous physiology of the merfolk) do not appear to be magical at all, these would be melee weapon attacks.