How reliable are rusty construction materials?

If you walk uptown, you’ll see a Toll Brothers staging area for the latest phase of the Maxwell Place construction. They stored materials like reinforcing bars (rebar) for quite a long time, and in all sorts of weather conditions (the feral cats loved ‘em though..)

Was wondering – doesn’t rust cause weakness in steel? Perhaps this is just another part of the planned obsolescence conspiracy so they can demolish and build again a few decades from now?