Sometime the words are easy, like I attack the Orc with the sword, and sometimes they are more difficult, like I try to talk my way past the guard by flashing some calf and giving him the bedroom eyes. The use of 'difficult' and 'easy' there indexes systemic differences more than anything else, as most system cover the first quite well, and many fail to cover the second in enough detail to make some people happy.
So while I generally agree with your framework and your description of the framework indicates you are following along, I think you are focusing on a very different issue than I've so far discussed.
Yes, it is true that when the rules leave open to the GM to determine what is an "easy" or what is a "difficult" challenge, that there is a table specific process for determining what actions goes into what categories. And yes, it is true that systems can offer insufficient guidelines to make clear to the table what the designer expected the GM to rule, which can cause a problem of play where different participants have widely different expectations about rules are going to be applied to a proposition.
But while that's all important process of play topics, that wasn't really where I was going with my example. My point was even more basic "
I try to talk my way past the guard by flashing some calf and giving him the bedroom eyes." can fall afoul of an unspoken proposition filter that renders it an invalid attempt to push the button.
That is to say, the result of the proposition might not be "Pass" or "Fail" but "Syntax Error". In this case, the proposition actually would generate "Syntax Error" at my table. The player indicated a desire to "talk" but didn't actually put any words in the mouth of his character. So while the player usefully gives me some indication of his character's fictional positioning with respect to body language, this proposition would tend to yield the response, "What do you say to the guard?" And only after the player provided the full fictional positioning, would the proposition be validated and the dice rolled to determine success.
Along these lines, there are also processes of play around non-proposition declarations, or what I call "calls". Are calls allowed and if they are allowed, which ones are legal? For example, different tables might declare all of the following allowable or none of the following allowable, or some combination thereof:
a) Player: "What is the guard wearing?"
b) Player: "Can I use my knowledge of Heraldry to determine who the guard works for."
c) Player: "The guard is wearing the sign of the Sacred Cudgel. As I am an initiate of that Faith, I try give him the secret sign of a fellow initiate in distress."
d) Player: "Earlier in the day, I put itching powder in the guards clothing."
Amazingly, almost all of that can be done as an extra rules process if the table agrees to it. While different systems may explicitly put rules around such calls, or explicitly declare certain sorts of calls invalid, most of them are actually silent on the issue simply because they never considered a call to be a possible part of play. And even those that implicitly assume a call like 'a' asking about the environment are a part of play, they don't really think about them. They just assume everyone knows they can ask the GM for more information or clarification about the setting, even if they aren't declaring an action to do so.