Trivially non-contradictory. Consider a hypothetical situation in which all the good skilled workers are on visa statuses that do not permit work and have missed the H-1B lottery. Both things are then true.
The comment isn't talking about local workers. It is talking about (a) foreign workers who are skilled, (b) low-wage less-skilled foreign workers and how the H-1B fails to achieve its stated aim in two respects because it's easy for there to be unemployed (a) and employed (b).
The comment contains no argument that local workers are being replaced.
