Inspector's Test 'Plug' Suggest No Ext. Discharge?

Does the requirement that a dry system Inspector's Test have a plug mean that it cannot be directly routed to an exterior drain?

NFPA 13 2022 Section 16.14.2 requires that the test trip connection on a dry pipe sprinkler system be equipped with a plug (or nipple and cap). The appendix then includes a detail of how the plug can be removed and a temporary connection can be made to the exterior drain for testing.

I can't remember having ever seeing that in person or in the design for an actual dry system.

Was it always there I was just never paying enough attention to the details?

Or is there a way (or ways) that the plug requirement is typically satisfied with a maintained connection to the exterior drain?

I had it in my head that equipment like the TestanDrain had equipment to fulfill that requirement, some sort of fancy hoses or something, but now that I've been looking into it, the hoses I'm seeing on there are all for pressure relief of wet systems.

Am I just remembering hoses that were kept handy but not actually connected except for testing?

The Meyer Fire blog post on inspector's test requirements even shows a combined drum drip/inspector's test, but I don't see how it fulfills the plug requirement.

What am I missing?

​Thanks in advance for any clarity.

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