Get participant data behavior

Similar to this issue found in this thread:

I am unable to fetch agent participant data when call is transferred directly to queue. I invoke Get Participant Data from the inqueue flow but I am not getting the AGENT participant data.

There is a custom click-to-dial apex code invoked from SF and it is saving the participant data under agent participant.

Question:

Does Get Participant Data only look at customer participant data or both?

If I use a data action to fetch the conversation's participant data it works. Hence the question above.

I'm trying to avoid calling a data action here to prevent increasing API limit usage.