I disagree. A network effect does not need to be inherent to the product / service itself. It can originate from other sources. What is the network effect of eBay? As a seller I do not care how many other sellers are there. But I care how many buyers are there. For a buyer it's the reverse. Buyers attract sellers and vice versa. That's a network effect too. For Atlassian it's similar. Jira customer attract Jira consultants and vice versa.

Ecosystem is the better word for sure. it's competitive advantage is still a network effect.