> A - they are replaceable and their work isn't that unique and B - they are the bottleneck, not the process or workload.

The problem rather is: often good programmers have quite good ideas how these problems could be solved, but for "organizational politics" reasons they are not allowed to apply these solutions.

Thus:

Concerning (B): Because they are not allowed to apply their improvement ideas, they are the bottleneck. But being the bottleneck is not the root problem, but rather a consequence of not being allowed to improve things.

Concerning (A): It is indeed often the case that if you simply let someone else do the work, the code quality decreases a lot and in subtle ways. Good programmers are very sensitive (and sometimes vocal) with respect to that - in opposite to managers.