As far as I understand, 1e-10 of relative accuracy is not really enforced in stats, especially where generic methods are involved [while I agree it'd be welcome to make it a bit more stringent here]. Eg, https://github.com/scipy/scipy/blob/master/scipy/stats/tests/test_continuous_basic.py#L349  (DECIMAL=5).

Having said that, the last commit bumps it to 1e-7 absolute, 1e-10 relative error.