It was a health advisory in 2022, and it was revised from .004 ppt (note that you are off by an order of magnitude) to zero. Per the EPA:

> Drinking water health advisories (HAs) provide information on contaminants that can cause human health effects and are known or anticipated to occur in drinking water. *EPA's HAs are non-enforceable and nonregulatory* and provide technical information to drinking water system operators

The update was because of additional evidence of cancers. The EPA always acknowledged that .004 ppt is not reasonably detectable, but the point of an advisory is to note the level that is evidenced to be dangerous. Its a goal, and the new goal is "as good as possible". It should be obvious why the EPA should set requirements to reduce toxins while also noting what is a safe level.

https://www.epa.gov/system/files/documents/2022-06/technical...