The code does draw some points. You see them, if you use a marker:
plot(linspace(0,bw,10), PSDnin1, 'o')
or with a line:
plot(linspace(0,bw,10), repmat(PSDnin1, 1, 10))
The documentation of plot mentions:
If one of X or Y is a scalar and the other is either a scalar or a vector, then the plot function plots discrete points. However, to see the points you must specify a marker symbol, for example, plot(X,Y,'o').