Approval voting is simple enough, but is vulnerable to bullet voting: approving an additional candidate can make your first choice lose. This makes it unsuitable if your goal is to make third-party voting more viable, which seems to be the premise of the article.
And, particularly, there is very notable cultural variation, which means (ab initio at least; over time, one expects behavior modification efforts would be deployed around this), support from different cultural groups in a diverse polity will have different electoral value even when turnout is the same.
> Approval voting is simple enough,
But also has the same problem: concretely what “approval” means is unclear and will be subject to voter-to-voter variation even when the actual preferences are identical.