"Systems Analysis And Programming" (62.2%) and "Computer Occupations, Other" (8.4%) are together 70.6% in 2017. That's the approximately the same population as "254k/365k of H1B petitions in 2017 were for computer occupations" which is about ~70%.

So 86% of of "Systems Analysis And Programming" and "Computer Occupations, Other" are "Systems Analysis And Programming".

If you want to assume "Computer Occupations, Other" are not devs, which is not a good assumption in my opinion then fine only 86% are devs.

In an informational bulletin, USCIS also stated that “Engineers may not fill computer-related jobs under TN classification unless they have credentials as computer or software engineers from institutions that recognize computer or software engineering as bona fide engineering specialties offering full engineering credentials, such as professional engineering licenses.” USCIS Employment Bulletin: NAFTA (2005).