Does any not pull their emergency trailer brake cable?

I think the OP's fear comes from the "experience" gained using the emergency brake in a vehicle... which if not "exercised" on a regular basis may result in the brakes remaining lockup as the e-brake cable and / or brake components are "seized" such that the system does not release especially with a "shoe based e-brake" system. Since the trailer system doesn't rely on a "long run" of potentially rusted cabling, it is unlikely that setup will stay locked up (spring failure maybe). Further of course, if a lock up occurs, your vehicle does not become "useless" and can still be driven to get assistance or otherwise where on vehicle brake lockup, you are pretty much toast.

As other have indicated, the trailer ebrake should be tested "regularly" and fear of lockup should be the least of your worries.