This is in the standards (when I did my 3* it was 60m):
This training programme aims at introducing the fundamentals of dive leadership to experienced certified CMAS Two Star Divers, which will enable them to plan, organise and conduct their dives and lead other sport divers in open water, to a maximum recommended depth of PpO2=1,4b + deep national regulation, meters in a safe and competent manner.
The question is of course, what is safe? But if you look at accident numbers in France where it is normal to dive on a 15 liter tank to 60m, it seems to be quite safe. I don't do such depths single tank and without decogases and I don't stay withing NDL. But I am not only in CMAS. I do trimixdiving also. Single tank to such depths is notdone in my eyes, I don't call it safe. But a lot of divers do.
A lot of countries don't have a national regulation, so then it is the 57 of 60m. Like in my country, but we don't have water deeper than 50m.
CMAS is an organisation that has a lot of local licencees. They have to follow the cmas standards, but sometimes things are different. In my country, 3* is NO DECO, and never goes deeper than 30m, but you get a CMAS 3* cert with the CMAS logo (Nymph), so it is the 60m. you can do here a 2* (aow) and never dove deeper than 20m. I will never sign such divers off as this is ********, if you don't want to dive deeper than 20m, stay open water diver/1*. And you get a 40m cert as it is an international cert.
There is another 'rule': 4.2.3 To conduct any specialised sport diving activities for which he has received appropriate training;
What is appropriate training? You can allways say I have, as training only means you did trainingdives, there is not said you need a cert or did it with instructor. And then you are allowed to do. This is cmas also.
Another way to skip the deep diver cert is not only by getting a cmas 2* cert (go from open water to cmas2*), you can also do: ow, aow, cavern, intro to cave. Intro to cave is most times a 39/40m cert. Even if you never went to such depths. But then a deep diver is not needed anymore.