My take is you should always just store any third-party data sources in your data warehouse, where you can then join it with all the other data. Having a feature like this just enables bad practices, and we'd rather be opinionated about how the data stack should look.
Since this is the "best practice" architecture, we've made the decision to focus on integrations with data warehouses specifically— Snowflake, BigQuery, etc. I don't think Chartbrew has these.
Oftentimes data teams have those data sources in the warehouse already (or a process for ETLing new ones in).
Copying data only once means lower costs (maybe) and fewer inconsistencies.
Plus if they’ve done work to join/clean/transform the data in the warehouse they can take advantage of that for product analytics without having to reinvent the wheel in ChartBrew or Mixpanel.