I apologize in advance for this sounding sarcastic, but I'm really not sure what it is you think Butler is talking about. Butler isn't talking about how physical traits make certain people more adapted to do certain tasks, so I'm not sure how you're addressing their arguments.

>It is very much the same as how someone with bigger muscle mass will end up lifting the heavy things and the short person will crawl into difficult to get into spaces. There is nothing of a performance in any sense of the word, merely people doing what they are naturally good at.

Note that Butler doesn't use the word performance, and this is important. "Performative" refers to an act which produces a series of effects. In a way, a person lifting a box is a performative act, but it is not necessarily a performance. And Butler doesn't argue that people are performing their gender, but that gender is constituted on performative acts that are essentially non-private.

>what Butler sees may be largely performative, but it is not entirely and solely performative, which is an incredibly difficult kind of case (the "all" structure of her argument, which I think may just be to seem controversial. She may not even truly believe it) to make for even the most modest of claims.

Note that Butler does in fact believe that this performative structure is pervasive, but is also arguing this on the basis of a particular cultural phenomenon, not an all-encompassing concept of gender. The point is that gender identity, as a classification, is essentially a public thing and so is something imposed on people, but not simply or solely imposed, as it is possible to break away from cultural conventions with whatever limited success.

I just want to emphasize two points, since I've been frequently recalling them in this thread and it seems clear that many commenters here are attributing positions to Butler that Butler does not in fact hold:

1. Butler is talking about identity, not some trivial form of classification that biologists (for example) construct in order to indifferently talk about certain things. Butler doesn't deny that bodies come with certain physical traits and properties and that these physical traits and properties effect how people are perceived, how they act, etc. What Butler is saying is that, insofar as this physical dimension contributes to an understanding of gender/sex identities, it is a social construction (= decided on in a public context, it does not mean that these classifications are simply fake). But identity is established socially, so that it moves into the everyday (into relations with family, coworkers, friends, strangers). Any analysis of gender that ignores the various ways that it is constituted is not a good analysis, and insofar as scientists are also people living in a society, they also have a pre-scientific understanding of gender which informs their inquiry.

2. Performativity is not performance. Butler is not saying that we go out every day and simply act out our gender as though it were a garb one wears or a role one plays on a stage. The term "performative" comes from linguistics and denotes a speech act which, instead of merely describing something, creates an effect. "Open the door" is a performative utterance. On this basis, Butler proposes that gender is a performative phenomenon since, as social system of classification, it is constituted and established in various acts (not only linguistic) which solidify a conceptual determination as if it were an inherent identity (e.g., there is a difference between saying "this person has manly features" and "this person is a man inherently, and expresses manly features due to that fact").