Update 2 / Solution:
So turns out using enable_queue=True in launch() doesn’t work, e.g:
iface = gr.Interface(fn=..., inputs=..., outputs=...)
iface.launch(enable_queue=True)

After looking at the source code, I saw that enable_queue is a deprecated argument in Inference()
Doing the following fixed the 60 second timeout for me:
iface = gr.Interface(fn=..., inputs=..., outputs=..., enable_queue=True)
iface.launch()