I guess I wrote that incorrectly. My Teric begins the safety stop counter once I have ascended shallower than 20’. I usually hang out around 15’ during my SS.
I think the answer to your question can be found in Teric manual pages 24 and 25, and prehaps better explained in Perdix AI "Recreational Nitrox Mode Manual" pages 14 and 15.
There is sometimes controversy related to meanings of "safety stop" and mandatory deco stop. But Shearwater has it's own definition for them.
In Perdix and Teric OC Rec mode (and only this mode) the safety stop timer starts only after mandatory deco stops are cleared.
Thus if you see NDL time replaced by a mandatory deco stop during your dive, you are obliged to hold it and it will be followed by a safety stop countdown.
Usually in typical NDL diving the 1 or 2 minutes of deco oblication at 10ft you see will "melt away" during your ascent. Thus when you reach your safety stop depth you actually do not have any mandatory stops to do and your safety stop timer starts immediately. Otherwise it is just fine to stop at 15-20ft and wait until your deco clears, it will just take a bit longer than at 10'.
Bottom line. In Shearwater OC Rec mode if you see "safety stop" countdown, you have already cleared your mandatory deco stops. Tec modes do not have safety stop countdowns.