DavidMBeetle wrote:
At first I thought you couldn't play MP3s added on a computer to apple music library through your phone...
You were mistaken. Thus there is neither a glitch or an update. The Apple Music app supports a number of audio file formats. Supported files can be transferred to a device over USB/local WiFi using Finder, or if you have a subscription to the Apple Music service they can be added to your iCloud Music Library, which is then available to any computer or device signed into the same service. MP3s may be uploaded as they are or matched with the same track in the Apple Music catalog. Depending on the details the cloud version may download/stream as your original MP3 content, or as an AAC (match/conversion) of the same thing.
Note that certain songs may be excluded from your iCloud Music Library. This can include, for example, songs that are too large, too small, have a non-standard bitrate, or were originally purchased by a different Apple ID.
tt2