This question is inspired by the following and stems from wondering whether the Steel Defender's "Force-Empowered Rend" action involves taking the Attack action:
Take the Lich for example, It has an action titled "Paralyzing Touch"; does this involve the Attack action? Similarly, the Ogre has the "Greatclub" and "Javelin" actions; do these involve the Attack action? Does the Adult Black Dragon's "Acid Breath" involve the Attack action? How does one know if something listed under "Actions" in a monster's statblock involves taking the Attack action or not?
This matters for various features that key off of taking the Attack action while somebody is polymorphed, shapechanged, Wild Shaped, or by some other means has become one of these creatures while maintaining their class features such as Extra Attack or the Monk's Flurry of Blows.
Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.
Immediately after you take the Attack action on your turn, you can spend 1 ki point to make two unarmed strikes as a bonus action.
The only thing I have managed to find that I think might be relevant is the following SAC ruling:
Q. Can you use a melee spell attack to make an opportunity attack? [...]
A. [...] A few monsters can make opportunity attacks with melee spell attacks. Here’s how: certain monsters—including the banshee, the lich, and the specter—have a melee spell attack that isn’t delivered by a spell. For example, the banshee’s Corrupting Touch action is a melee spell attack but no spell is cast to make it. The banshee can, therefore, make opportunity attacks with Corrupting Touch.
Note that this question is different from my previous question:
The question failed to ask what I actually wanted to ask. It happened to be asking about an action that could effectively be accomplished through unarmed strikes and was not explicitly asking about things like the Lich's Paralyzing Touch and a Dragon's Breath. This question, in contrast, is asking about such features explicitly.