i) After googling 'What is a college degree? I copied this from Wikipedia.
The parts in red might well not be recognized by the Chinese as suitable academic qualifications for FTs! Hence no Z visa issuance!

A college degree is certification...

A college degree is certification of completion of state and/or federal educational requirements.
The degree informs the public that you have satisfied the necessary requirements to be considered a graduate of one of the various levels, or "degrees", of educational attainment.

An Associate's Degree marks the completion of two years of college

, a Bachelor's marks four years, and a Master's Degree or Ph.D marks a continued level of education beyond a Bachelor's.

*An academic title...

...given by a college or university to a student who has completed a course of study.

Or,... a similar title conferred as an honorary distinction".*

American Heritage Dictionary

In military terms
Consider High School graduates as (Private).
An Associate's Degree (Corporal) usually takes two years to complete.
Earning a Bachelor's (Sergeant) takes four,although some finish the curriculum in three and a half years.
A Master's (Lieutenant & Captain) usually takes two years or so.
Doctorates (Major, Colonel & General) vary in lengths of time.

4-year college graduate

Most of the time, the term "college degree" means a Bachelor of Arts or Science Degree from a 4-year college or univerity.
Of course "college degree" can refer to higher and lower levels of education that are also marked by "degrees".

ii) I beg to differ with you re being powerless if you've been employed illegally. Fact is, you're the boss - you can pull a runner and they can do absolutely nothing. Or you can threaten to go to the relevant authorities to make big trouble for them if they've dared to break their illegal contract with you! If you have money, you can dare to pull this one, then watch 'em squirm. It has worked for me invariably, both before and after marrying a Chinese lady.