There is no rating credit for "non-engine" in PHRF..... unless you are talking about inboard vs. outboard. Olsons in general do not have an inboard.
The <125% jib credit used to be 6 sec/mile and in the late 90s(??) PHRF lowered it to 3 sec/mile.
The only rating adjustment the SSS uses is one developed for the PacCup..... which again takes into account planning vs. non-planning hulls (ie how heavy the boat is). This is very similar to the Downwind ratings that have been developed by the PHRF.
In 2018 the Olsons were the fastest boats in the fleet which is very rare. However sailing an Olson is no guarantee of success.
Please take a look at these historical results which have Olson 30s all over it.
http://sfbaysss.org/shtp2018/2018/07/17/forty-years-of-shtp-results/
I'd say based on the 21x times I count the Olson 30s have competed in the race it hasn't done very well at all. The overall winners seem to be NOT Olson 30s.... in fact it seems displacement boats have a better chance.
Here are the overall winners I gathered:
Islander 36, Cal 40(2x), Olson 30(3x), Wylie 27, Wilderness 30, J/120, Erikson 35mkII, Spenser 35, Black Soo 30, Baltic 38, 30Sq.Meter, Newland 36, Freedom 44, Carlson 29, Wylie 34, Golden Gate 25, Santa Cruz 27.