This chap has apparently made an error of judgment. Now there are not many who I would think would go to work intent in deviating from SOP's to a point that puts you out of a job. For that reason I sympathise with this guy/girl. But I am not aware of the case or details so perhaps my sympathies are unfounded. At the end of the day it appears they (the captain) did not follow SOP and paid the ultimate price.
Now for your purposes.
Let's go on, shell (sic) we? SOPs continue by saying that if the a/c is not configured by 500' then the (PNF) "Must" say, "Captain You Must Go-Around!" What is ambiguous about that?
I would suggest you keep up to date on your SOP's. The March 08 Boeing ops manual did indeed have the command "Captain You Must Go-Around". Now in your defence this would probably have been the governing authority in use at the time of the event (only a guess, please forgive me if this is in fact incorrect). But the update effective 10th July does not differentiate between who is PNF and merely states "Not stable go-around". I must say I prefer this later one as I think the previous SOP was rather vague. This is now quite clear and succinct. But to conclude, "ambiguity" is sometimes not as straightforward as it seems when dealing with complex manuals.