“White Paper” (WhitePaper, WP) is a document that describes the key features of the project. This document usually contains a detailed description of the main indicators and characteristics. The mere presence of a quality White Paper doesn’t guarantee the success of the project. It was an important document for ICOs, because as a rule WhitePaper was the only active they had.
Hence a WhitePaper is not necessary for STOs, they still can publish it. But it can be named in different names – Presentation, Pitch deck etc. It doesn’t matter how it is called, more important is what it contains.