Yes, I know. But this is not correct. I have looked in the code and it does not accept a modifier in the dice string - which is why you get an error if you include a modifier.
damned is not so proactive in updating his documentation! For example, there are two entries here for /sthrow: https://www.diehard-gaming.com/mchelp.html#rolls One with modifiers (v1.36) and one without (v1.37) - the second is correct.