I think it's pretty common that when someone says "nobody does X", that's shorthand for "there is probably a very small number of people who do X, but not enough to make much of a difference".

Sure, there are some people who abuse WFH, but I suspect it is far fewer people than Zuckerberg and Pichai suggest, and there are other, more important reasons for productivity losses. Reasons that have more to do with management and poor strategy than the actions of individual employees.