Focus mode not working with 3rd party wearables

I was very excited to try out the new focus modes in iOS 15, but only to realize that it doesn't work right with 3rd party smartwatches. I own a Garmin Venu and a Fitbit Versa and both exhibit the exact same behavior:

• If you set any focus mode other than the old "do not disturb" (e.g. personal, work), unwanted notifications are muted the others are allowed on the iPhone as expected, but no notifications at all appear on the watch, even those allowed. The granular modes basically behave like the old DND.
• On your iPhone, if you swipe left on a notification and choose "mute for 1 hour/a day", the phone again behaves fine but the notifications still to through and appear on the watch.
• Turning off or on the "share across devices" option has no effect. Neither Fitbit nor Garmin have options in their apps specifically for the new focus modes.

I don't see anyone complaining about this. Is there something obvious that I'm missing? Or are the focus modes only intended to work with other Apple devices? I appreciate the help as I use my personal phone for work and it's driving me crazy that for me it's still all-or-nothing when it comes to notifications.

I have an iPhone XS and I always install major iOS releases from scratch.