Breadboards and ground loops
The only real problem with that statement is that it doesn't give any context.  It certainly isn't true for high frequency circuits, but perhaps they figure that if try high frequency circuits on a breadboard you'll have bigger problems anyways.

Basically there is so many other crappy aspects of breadboards (trace to trace coupling, additional capacitance, poor connections, loops of wires ...) that this is the least of your worries for doing performance circuits.

But people do circuits on tose all the time and get results so there obviously is a usefulness to them.  In this case it really isn't an issue with whether or not it is bussed, that bus in there can probably handle amps it is the connection to the bus that is the issue.

Most of the frequencies that you deal with on circuits that can run on breadboards are modeled by lumped circuit elements so the distribution of wiring plays less of a factor.

The author should have really stated the limits and their assumptions to avoid that being too broadly applied.