Thank you.
Because it is an attachment, my application isn't responsible for the video player - that is native functionality for uploaded video files, added by Invision several major versions ago.
Why is it a video player instead of an audio player? Because Invision have .ogg files listed in their $videoExtensions variable in /system/File/File.php:
/**
* @brief File extensions for HTML5 compatible videos
*/
public static $videoExtensions = array( 'mp4', '3gp', 'mov', 'ogg', 'ogv', 'mpg', 'mpeg', 'flv', 'webm', 'wmv', 'avi', 'm4v' );
...and they also have it listed in their $audioExtensions variable too:
/**
* @brief File extensions for HTML5 compatible audio
*/
public static $audioExtensions = array( 'mp3', 'ogg', 'wav', 'm4a' );
When a file is uploaded, Invision is checking it's type and then deciding what to do with it...and because it first finds ogg in the videoExtensions list, you get a video player.
How to fix it? Go here or here and post about it - it would help to link to this post so that whoever reads it doesn't simply say "OH, disable this or delete that or contact the dev"
For information - my application is only having an effect on the native player by turning the embedded video player (added by Invision) into a linked attachment because both the "Enforce settings to native IPS video" and "Enforce 'Download attachments' permission" settings are enabled (reason for using those is in the linked description of the second setting)