Perplexing documentation for API method

[A248]

I was browsing through the BanManager API and came across this statement in the javadoc:

BanManager/common/src/main/java/me/confuser/banmanager/common/api/BmAPI.java

Line 472 in acb1ef1

* This method is not thread safe and should not be called on the main thread.

It is mostly obvious why such a statement is confusing. If an API method should not be called on the main thread, but is not thread safe, what thread should it be called on instead?