It’s likely that many podcast hosts could incorrectly credit downloads from Google’s new iPhone app to Apple Podcasts. Unlike the "GSA/" user-agent of the Android app, the iOS app has a user-agent of "Podcasts:"
Thanks for the heads up, James! We were able to update our list of user-agents and deploy an update today.
Now, your podcast analytics on Transistor will also include listeners who use Google Podcasts on iOS: