I'm surprised it doesn't work for you either. Testing in the sandbox returns the correct results every time. Here's my request in CURL:
curl -X GET -H "Content-Type: application/json" -H "Authorization: Bearer <<my token>>.t" -H "Cache-Control: no-cache" -H "https://sandbox.jiveon.com/api/core/v3/activities?count=25&filter=verb(jive:created)&fields=verb"
Looks like the count filter may be hiding the incorrect results. I tried bigger page sizes and found a number of invalid activities (jive:replied and jive:commented) in this batch.
I just looked into my postman history, and I was using a count of 1000 as well.
I pasted the api query with a count of 25 here to simplify ... let me change it
Thanks for bringing this up!