I am experiencing the same issue right now. I am still awaiting a solution.

Sounds dumb but, for whatever reason, the built-in Area parameter in Floors isn't available to Tag.

Creating a Shared Parameter called Area with Type of Parameter set to Area doesn't automatically pull the area of an object being tagged. Area as a SP is just a name (could be called Josh) and doesn't have to do anything with the thing being made parametric (though it helps).

Best bet, short of coding, is to create a SP called something like Area_Tagged and to manually fill it in to match the area of the floor. You can speed this up a bit by creating a schedule of Floors with the built-in Area parameter and your new SP as the only two columns and then copying from one to the other.

Of course being a manual process means you'll have to keep you eye on changes to the floor as they won't update the tag.

Does anyone know something about read-only parameters and writable parameters? I guess system parameters are read-only parameters (they automatically pull the parameter of an object being tagged) and all new made shared parameters are writable (we have to manually fill the value of parameter in object properties)?

What do you want to know about them?

Not all system parameters are available to be tagged/filtered/etc.

Workarounds are the norm for now.

I want to understand better the issue and program in general. Is there any tutorial that are explaining this more?