Popular Deck Building Board Games (Mechanic)

So, this is a little bit in response to the recent post by @Skurvy5, lauding the joys of engine building. And, to be clear, I am not knocking that post..... I think it was a good post, and I believe that it fits well into this weeks challange. But, my question this morning is, Is engine building a mechanic/mechanism?

BGG famously does not have engine building as a mechanism. This outraged many people, including myself, upon discovering that fact. I considered it almost a criminal omision. However, as time has gone on, I have gradually come around to not having it as a mechanism. This is why I didn't include it in my list of favorite mechanisms here.Otherwise it would have been my favorite mechanism.

I have not read the "official" encyclopedia that defines all the mechanisms. And, I have not really studied why Geoff Englestien has declined to list it as a mechanism. The following thoughts are purely my own.

I think that the problem with having engine building as a mechanic is that it generally going to be another mechanism. For instance. I would argue that currently the vast majority, or maybe all, tableau builders are engine builders. In fact, if you go the bgg page for tableau building this is what it says:

"In Tableau Building games, each player has a visible personal array or tableau of components (cards, tiles, player boards, etc.) which they purposefully build or manipulate throughout the game by spending actions and/or resources (including opportunity costs) and which determines the quality, quantity, and/or variety of actions to which they have access throughout the game.

The array is not merely a place to store resources, to plan out actions, to store a puzzle which must be manipulated, or something that impacts VP's. It impacts the quality, quantity, and/or variety of actions which are accessible to a player. This means that some games may include an array or a tableau but not really be a tableau building game."

This really does sound like it is describing a engine builder, especially where it mentions, "the quantity, quality, and/or variety of actions."

If we consider the games that are popularly considered engine builders, including the ones mentioned in the recent post by @Skurvy5,we discover that they engine building parts of them are tableau builders/manipulaters. This even includes games like #Scythe. In scythe your tableau is your player board, and you are manipulating it to change the "quantity, quality, and/or variety of actions."

I don't think that most deck builders are engine builders, but, if they are than that compounds the problem. If all deck builders are encapsulated in some form or other of tablaeu building/manipulating, you could perhaps argue that engine building is a subset of that. But, if deck building, or other mechanisms, also have engine building, then it quickly feels like the mechanism is too big. For a the breakdown of mechanisms to be helpful it must be discreet enough to be helpful, it has to be broken down to a the smallest common denominator. If this is a mechanism that spans other mechanisms, it goes from a game mechanism to a game type. By game type I am refering to how we refer to the boxes we put games in, I am refering to terms like "confrontational" or "multi-player solitaire" or "euro" or "ameritrash."

So, in my way of thinking, either engine building is tableau building, in which case, that terminology is actually a little more helpful than engine building. Or, the term engine building is to big to be used as a mechanism. And should be used as a box like any of the multitudes of other terms we use.

Also, to be clear, I do think that engine building exists. I even think it is a helpful term. I just don't think it should be defined as a mechanism.

So, what do you think. Do you think is mechanism? Or, do you think that it isn't?