On this plugin test I can see there's 110 Flutter-iPhone simulators, some still booted before the tests run https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8787351356520040209/+/u/Run_package_tests/list_simulators/stdout. That could cause issues like running out of disk space.

The plugins tests should try to delete any simulators they have added.

Also a good idea to add api.os_utils.shutdown_simulators() to the recipe so at least they aren't booted:
https://flutter.googlesource.com/recipes/+/refs/heads/main/recipes/devicelab/devicelab_drone.py#203