Great question, not sure.
We just went to Unite 2018 and they announced some updates to that particular feature.
The "new" Shopify Flow allows you to easily automate tasks around inventory, ordering and customer loyalty.
The offering was announced a year or two ago, but this year, they’ve added something called connectors. It’s been glossed over but the media, but could actually be a huge deal for merchants.
Here’s what Connectors does. Instead of just being able to create automated flows based on the information Shopify has, you can now create automated flows by the information that your apps have, and then trigger actions within your apps.
Anyway, more on this on our blog, might be helfpul in answering your question: https://bit.ly/2LgASBU