You assessment is correct. The endpoint to get all configured simulators in a tenant is
/service/device-simulator/simulators
However I need to add a caveat here:
This endpoint is not in the public documentation, so none of the typical backwards compatibility guarantees apply. This means that anything in this endpoint is subject to changes. Context path and body formats may change in the future without prior notice.
At the moment we are not planning any concrete changes, and of course we are not going to change this endpoint just because we can. However, if a change would be beneficial for a bugfix or functional change we would not hesitate to implement it. So ultimately I can only recommend using this endpoint to a limited degree.
There are several other endpoints in this service and in other areas that are also undocumented. These rules apply to most of them.