I don't know if there's an implicit assumption that WFH is less productive, quite possibly. But if we look at the power dynamics of the question, it's about (tech in this case) labor being able to demand what it wants when it's in demand. I think the point above is that this dynamic will change with the economy going south.

With labor having less power, it's likely that the members of senior management who don't like WFH (for a multitude of reasons right and wrong) will have more sway in the conversation.