I'm trying to confirm this as I cannot find any documentation to indicate one way or another.
I have an app that currently has several Shopify webhook handlers configured to work with GCP PubSub. These work as expected and I'm successfully receiving all expected events. However, I was doing some local development and tried creating a new app with the same webhook handlers configured as my first app but these events are not coming through (however, the webhook registration indicates that there are no issues). Curious if it was due to the suspected uniqueness, I did try registering a webhook handler for a new topic that I knew was not already registered in another app and it did work.
Example: I have a topic in a GCP project xxx-orders-paid, I register a Shopify webhook for ORDERS_PAID to this specific topic in my GCP project for "app-1" and I'll get any ORDERS_PAID events sent to all subscribers of that topic when a store has "app-1" installed. If I create "app-2" and register a Shopify webhook for the same GCP project and topic, any store who installs "app-2" will say there are no issues when registering the webhook, yet when a store with "app-2" installed has new ORDERS_PAID events, no messages are published to the topic.
This is important as we need multiple developers to be able to develop locally and simultaneously with end to end functionality without direct access to the apps within our company's Shopify Partner account.