The worst RRF of any guy with SS as his primary position and 500 PAs is 1934 Woody English with a 3.06. That is SUBSTANTIALLY better than HoJo's 2.65. Interestingly, English is an A/A+ 3rd baseman.
The 2nd worst RRF of anybody with 500+ PAs is 1890 Ray Irv's 3.71, and there are only 6 guys below 4. So it may in fact be reasonable to assume that HoJo falls outside of the range of RRFs that were used to set the curve for +/- plays at SS. His expectation value for - plays could well be north of 30. The average in the Performance History is 29, but it's tough to understand that. It lists 145 games played at SS as average, but the sum of all the listed defensive games played is way too high, and until quite recently moving guys mid-game was impossible, so I have no idea how many games he's actually averaging 29 - plays in. Maybe it's 145, maybe it's really more like 110 or 120 because of some teams playing him at 3B or somewhere else, which apparently happens...