Can HealthKit app sync data input from two iOS devices?

I still use my iPhone 4s at the gym because it is smaller has a more rugged case, is older and I don't need cell service at the gym. It has wifi for Messages and syncing Jefit app which all I need or want when I'm there. I use the Wahoo Fitness app to monitor my heart rate while doing cardio and it feeds into Health on that iPhone 4s just fine. The problem is none of that data shows up in the Health app on my iPhone 6. Health on the 6 updates fine with Sleep Cycle and myfitnesspal.

I use the 4s in airplane mode with wifi on, essentially turning it into a iPod touch.

Both devices are backing up to the same iCloud account and using the same Apple ID. I'm not using iCloud Drive and will not until Yosemite's wifi is reliable enough to upgrade my MacBook Pro from Mavericks but I wouldn't think iCloud Drive would be required for this activity.

If this isn't possible it should be. The Health data should sync across devices using the same Apple ID.