Subfield $c is not repeated when the fields would be adjacent to each other. That LC authority is incorrectly formulated and probably should be revised to:
Wang, Wei ǂc (Law teacher and writer on industrial laws and legislation)
"Writer on industrial laws and legislation" would be considered either an occupation or an other distinguishing characteristic. The field of activity would just be Industrial laws and legislation.
Subfield $c is repeated when something else is in between the two subfields, as in the AACR2 example Black Foot, $c Chief, $d d. 1877 $c (Spirit) or this RDA one: Lodge, Oliver, ǂc Sir, ǂd 1851-1940 ǂc (Spirit)
The MARC 21 format itself specifies that you don't use two consecutive subfield $c's. See https://www.loc.gov/marc/authority/adx00.html, where it says:
Multiple adjacent titles or words associated with a name are contained in a single subfield $c. Subfield $c is repeated only when words associated with a name are
separated by subelements contained in other subfields.
University of Washington Libraries
When it is necessary to identify a person by two professions or fields of activity in a qualifier, are these terms entered into a single $c or in separate subfields?
For example, there is this name authority record by LC, where the two :
040 DLC ǂb eng ǂe rda ǂc DLC
100 1_ Wang, Wei ǂc (Law teacher) ǂc (Writer on industrial laws and legislation)
Are there separate $c subfields because "Law teacher" is technically an occupation and "Writer on ..." is a field of activity?
There are a lot of existing authority records where the professions/occupations/etc. are enclosed in a single subfield, such as:
100 1_ Smith, Simon ǂc (Teacher and poet)
The MARC authority format allows for repeated $c subfields, but the example given shows different types of usage (different types of titles and other terms):
0_ $a Black Foot, $c Chief, $d d. 1877 $c (Spirit)
I cannot find instructions guiding us to a preferred method. I do not see an example in RDA (and LC-PCC PS) 22.214.171.124. Should the Smith example above be?
100 1_ Smith, Simon ǂc (Teacher) ǂc (Poet)