A couple of things that "they" say seem to contradict each other.
- A safety stop is not a decompression stop.
- Every dive is a deco dive.
When I first learned to dive, there were no safety stops. We just dived, ascended slower than our bubbles and got back in the boat. Today I see people do 20 mins at 20' and then do a 3 min safety stop. Both kinds of diving show a lack of thinking through the reason for ascending at a specific rate.
Off gassing doesn't suddenly begin at 15'. And you can't off gas what you haven't on gassed. The goal is to get out clean - breath off the excess nitrogen below the surface. And there are many ways to do that.
GUE has an excellent system that has a diver beginning the off gassing process at 80% of max depth and then doing short stops every ten feet on the way up.
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The "safety stop" is not a deco stop, unless you need it to off gas so you can ascend safely, and that would be dive specific.