That is not necessarily true. Under some circumstances it can be true. For example, if a community builds more luxury apartments entirely in addition to existing apartments, then yes some well paid people will probably move out of the existing apartments into the new luxury ones, making apartments available to the lower paid.

However, if inexpensive apartments are either bulldozed or remodeled to become luxury apartments, eliminating inexpensive options for the lower paid. That has been happening in Mountain View and probably in San Francisco which the Guardian article directly discusses.