This is what they have replied for the issue :-
Thank you for reaching out.I tried it on my end and this seems a bug. I have logged it. Unfortunately, there isn't a workaround for this bug.The JIRA# is RIA-6725.
I have a comment on RIA-6725. According to the documentation - https://support.smartbear.com/readyapi/docs/testing/integrations/postman.html .
ReadyAPI currently supports only v1 collections and does not support v2 collections. So, RIA-6725 was converted to improvement request RIA-6640.
Export collection as V1 option. it works though deprecated.