Currently, all announcements sent to the RSS feed are copied to Discord. There is no way to differentiate between announcements sent to "All sections" and to specific lab streams on Discord, this means that announcements that should be for a Lab stream may get sent to Discord.
This can be partially mitigated by checking multiple RSS feeds for a single course from multiple people, hopefully in different Lab streams, then checking for new announcements that are present in all of the people's RSS feeds. This is however not implemented yet.