It shouldn’t be surprising. We’ve discussed this issue in the past.
Any ZLL device is supposed to, per the standard, be able to “fall back” To ZHA if paired to a ZHA coordinator.
Consequently the bulbs paired directly to the SmartThings hub, whether they are from Osram, Cree, GE, or Hue Will fall back to ZHA. They continue to self identify as ZLL, but they are functioning as ZHA devices.
That then brings up the whole question of repeating. Technically, these bulbs should act as ZHA repeaters When on power, and community members have posted Zigbee maps for over a year showing that that does sometimes happen.
So why only sometimes? As best we can tell, there seems to be a timing issue with the bulbs, and they just don’t always succeed in repeating.
We have a community FAQ on that. @vlad might find it interesting as well. 