This policy setting allows you to control the redirection of supported Plug and Play devices, such as Windows Portable Devices, to the remote computer in a Remote Desktop Services session. By default, Remote Desktop Services allows redirection of supported Plug and Play devices. If you disable this policy setting or do not configure this policy setting, users can redirect their supported Plug and Play devices to the remote computer
Read the full blog post: https://calcomsoftware.com/the-policy-expert-rds-do-not-allow-supported-plug-and-play-device-redirection/