That’s not true. There’s an API to read from and write to Apple Health: https://developer.apple.com/documentation/healthkit

I’m not sure if that’s something the Pebble app uses right now, but it’s certainly possible, and a third-party app could make it happen as well.

My Garmin syncs its data to Apple Health. I don't see why Pebble wouldn't be able to do it. My understanding of the post is that it mostly refers to internal iOS APIs that are not available to third parties (e.g. actionable notifications).

The Pebble 2 could write data to Apple Health ten years ago. It would be surprising to have that missing now.