It makes sense as long as it isn't 4th and long.
Last year SD St on 3rd and 1-3 yards to go, averaged 6.17 yards per play. If they were able to get similar on 4th downs then they should go for it with 1-3 yards to go. On 3rd and 4-6 yards to go they averaged 4.92 yards per play. If they were able to produce similar on 4th down, then on average they would convert with 4 yards to go but fail on 5-6 yards to go. Then there is 7-9 yards where they averaged 4.98 yards, and 10+ where they averaged 8.47 yards. In both cases they would fail to convert. So assuming similar results on 4th down, SD St should go for it when they need 4 yards or less. And that's assuming that the added pressure of 4th down doesn't bring those numbers down further.