I had a feeling of a twist just because initially I found https://support.getpostman.com/hc/en-us/articles/203815791-W... which gave me impression that they do not collect payload under any circumstances.
I would hope that they add a clarification in that page because if I did not contact them then I would not have know about the sync feature and also would not have thought anything about GDPR issue. This is just a reminder note, not saying that Postman is hiding about it.