Dir.glob returns inconsistent results inside memfs

[omohokcoj]

irb(main):176:0> Dir.glob('{*,*/concerns}', base: '/__enclose_io_memfs__/local/app')
=> ["assets", "channels", "controllers", "helpers", "javascript", "jobs", "mailers", "models", "views"]

*/concerns subdirectories are missing when searching for directories in mounted memfs but present when using a local fs:

irb(main):063:0> Dir.glob('{*,*/concerns}', base: '/Users/pete/Documents/rails-pg/app')
=> ["mailers", "models", "javascript", "jobs", "controllers", "views", "assets", "helpers", "channels", "models/concerns", "controllers/concerns"]

Looks like the issue is caused by pattern {*,*/concerns} because */* pattern works as expected:

irb(main):019:0> Dir.glob('*/*', base: '/__enclose_io_memfs__/local/app')
=> ["assets/config", "assets/images", "assets/stylesheets", "channels/application_cable", "controllers/application_controller.rb", "controllers/concerns", "helpers/application_helper.rb", "javascript/channels", "javascript/packs", "jobs/application_job.rb", "mailers/application_mailer.rb", "models/application_record.rb", "models/concerns", "models/item.rb", "models/test_column.rb", "views/layouts"]