Question: This question has come from a conversation at loggerheads. I can't find the answer online.
There are two positions on which is the correct expression to use when starting a job.For the example, I've used a job as a plumber.

Person A states "John becomes a plumber today"
Person B states "John has started working as a plumber today".

My understanding is that person A, while it is used in causal conversations is incorrect because it suggests a changing into something when they haven't changed, they added something to who they are. A job.
Can someone please advise which is formally correct and if using becomes is still incorrect use of the word or how they fit together.

Answer: 
Considering this is the part you're talking about:

> 
> I stopped watching for ridicule, the scorpion's tail hidden in his words. He said what he meant; he was puzzled if you did not. Some people might have mistaken this for simplicity. But is it not a sort of genius to cut always to the heart?
> 
> 
> 

I believe the narrator is trying to say that he has stopped watching for any hidden intent in the words of the person he/she is talking about (presumably Achilles). *That he speaks directly, striking at the heart of what he wants to say and does not attempt to beat around the bush or try to get his point across in an indirect manner*. Used in a manner similar to "cutting to the chase" in a way.
Quote
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I haven't read the book but I searched for the line you are mentioning on [goodreads](https://www.goodreads.com/work/quotes/16176791-the-song-of-achilles). This is the complete quote:

> 
> *I stopped watching for ridicule, the scorpion's tail hidden in his words. He said what he meant; he was puzzled if you did not. Some people might have mistaken this for simplicity. But is it not a sort of genius to cut always to the heart?*
> 
> 
> 

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Piecewise Explanation
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> 
> *I stopped watching for ridicule, the scorpion's tail hidden in his words. He said what he meant; he was puzzled if you did not.*
> 
> 
> 

This means that the narrator earlier used to take *he's* words as a ridicule - comparable to a scorpion's sting. But not anymore. Narrator has understood that *he* only speaks his mind. *He* is so simple (naive maybe) that *he* doesn't know that others don't always do the same.

> 
> *Some people might have mistaken this for simplicity. But is it not a sort of genius to cut always to the heart?*
> 
> 
> 

The narrator explains that while some people think that this behavior can be classified as simplicity, yet as per narrator this behavior is actually the quality of a genius person to speak what you mean and cut away all the fluff from what is really important.