Ha! I've been using this on my Garmin Vivoactive 4 for weeks now and works as expected. I'm diabetic T2 and use the Dexcom G6. Didn't know this was "new." But, since you need your phone within range for this to work, it's just as easy to grab my phone and look at the display.
The Dexcom Connect IQ app for Garmin devices is rolling out to provide "expanded region availability". The app allows you to track your blood sugar levels on a Garmin smartwatch or bike computer alongside other training insights. However, you must purchase a Dexcom CGM system and have your smartphone nearby to view the transmitted data.