Shouldn't each of the 38 melachos ALSO be considered “מכה בפטיש”?

Question

It seems to me that one could argue that every melachah has an element of "מכה בפטיש" (final hammer blow/ completing an object by applying the finishing touches) to it.

As OU Torah explains:

The melacha of makeh b’patish literally means the strike of a hammer but it refers to an act of completion. Any act of perfecting an object or rendering it fit for use is considered makeh b’patish even if it doesn’t involve a hammer (or any other tools).

It would appear that each of the other 38 melachot seem to contain an element of makeh b’patish to them. For example:

• Erasing (מוחק)- if one erases a whole sentence, right as they finish erasing it should be a violation of erasing and the final hammer blow

• Sanding (ממחק)- if one sands a doghouse, they should be in violation of sanding and (upon completion of the house) the final hammer blow

• Sewing (תופר)- if one sews a garment they should be in violation of sewing and (upon completion of the garment) the final hammer blow

• Selecting (בורר)- ex: if one separates the desirable portions from the undesirable portions and thus making an inedible food become edible, they should be in in violation of selecting and the final hammer blow

Why isn't one ALSO violating makeh b’patish whenever they violate any of the other 38 melachot?

Answer 1

Meiri to Shabbat 104b:

If one writes a single letter and thus completes a book, or weaves a single thread and thus completes a garment, one is liable, because any act which completes something is important, and is considered as if it were two [letters] and he is liable for writing.

The Sages of the generations have asked well: Why is he not also liable for makeh befatish...?

[The answer is that makeh befatish applies] only in a case where the work has already been completed, such as a stone that has been completely quarried and detached from its surroundings, so that the work of the stone is complete but it has simply not yet fallen. When the person strikes it with a hammer and causes it to fall, the work on the object had already been completed...

But in these cases, the book and the garment had not yet been completed, and any work done to complete something is not makeh befatish. If that were not the case, any melachah where the beginning and end come together, such as harvesting etc. also ought to make one liable for makeh bafatish.

(My translation, see the link above for the original Hebrew)

As I understand Meiri, makeh befatish can only apply when one performs the finishing touches to a complete, already essentially usable object.

Almost by definition, and certainly in your examples, if one is performing a different melachah to an item, then it is not yet complete, and thus makeh befatish cannot apply in addition.