I need that you read my first post as there is some misunderstanding.
I agree with what you posted, but it is not what I said at the beginning. It's obvious that if you get the visa approved and you were not working in the nominated position, you must stay for 2 years after your visa is granted and/or starting to work within 6 months from the day of your approval.
Moreover, I cannot understand how an employer could sponsors someone who's not working already for his/her business...
I basically said that if you start to work for someone who sponsored you with a full time contract signed as required for the 187, and you got your visa granted after 25 months, you have reached the requirement of 2 years.
Example:
Started to work in the business as casual in Jan 2015. Employer happily gives you the sponsor 1 year later in January 2016. Your migrant agent prepares the documentation required such as the contract full time signed on the 15th of January 2016 (this is when you commence to work full time for visa purposes). Rcb, Nomination and visa with all docs ready to submit on the 15th of Jan 2016.
Nomination and visa granted 25 months later, on the 15th of February 2018.
You satisfied the 2 years requirement, so you can leave giving of course the right notice period of time to your employer.
At least this is what the immi dept said when I called them, and my agent confirmed.