Yes, WCAG are guidelines, but they are not just suggestions in a lot of cases. WCAG has been adopted as the standard for a variety of regulatory purposes. For

Yes, WCAG are guidelines, but they are not just suggestions in a lot of cases. WCAG has been adopted as the standard for a variety of regulatory purposes. For example, with Section 508/504, the US Access Board requires procurements to be compliant with WCAG 2.0 AA. Germany’s BIVT is harmonized with WCAG 2.1 AA, California requires state entities and procurements comply with WCAG 2.0 AA, etc. At least in the US, the main sphere where WCAG has not been specified as the regulatory standard is with Title III places of public accommodation. However, Federal Courts have repeatedly upheld that places of public accommodation must make their websites accessible, they just won’t say how to accomplish that (nor is it their job to). In the case of GitHub, I can tell you with 100% certainty it has been provided to, at least, the Federal government as part of a procurement, is subject to Section 508 statutory requirements, and WCAG 2.0 AA is the required standard. This is to say, it might not be a good idea to arbitrarily decide that color contrast sufficiency is just a suggestion.