You may want to post your question to the dedicated EX2 subforum as this forum is generally for the single bay My Cloud devices.
https://community.wd.com/c/network-attached-storage/wd-my-cloud-ex2
Typically a DLNA server (at least those I’ve used) will always the Title metadata tag when a DLNA client displays the file when that metadata tag is available. Only when there is no title tag entry does the client use the file name (minus the file extension). Typically when one has a media device like a SmartTV that is capable of accessing videos on a USB device, it typically is NOT using DLNA since to use DLNA requires the use of a DLNA server for aggregate the media content to display to DLNA clients. Rather the TV uses a basic form of a file manager to access and play the file. It typically doesn’t access the file’s metadata tags rather just displays the file name.
The following link has general information that is useful if using the Twonky media server that is embedded into the My Cloud devices.
https://community.wd.com/t/faq-twonky-dlna-media-server-setup-use/95373
