Sorry, but I don't see the meaning of this example: adding a covariate drastically reduces the sensitivity of the test ? Actually, it does so for a bad reason: it has not been centered, hence it competes with the intercept to fit the mean signal in the data...
If  you want to make this example meaningful, center the covariate and test it instead of testing the intercept.

Moreover, I think that there should be 2 examples instead of that one:
- one "data example", that shows how to use the localizer dataset, with simple methodology (classical t-test, no permutations)
- one "methods example", that compares permuted OLS with standard OLS. (and then other examples for RPBI, robust regression etc.)