When and administrator pins a top the Workplace API does not make this visible. These posts of topics will not be counted in SWOOP and if only used in this instance not searchable.
We have raised this with Meta and they consider this to be a feature which they have put in their roadmap. They don't agree that the incorrect reporting of topics in their API is a bug.
If this is important to you in SWOOP you must include the topic in a post before pinning it.