I am familiar with your concerns and have had this issue with my LG Watch Urbane (1st edition). However, there is a solution.
First, you need to turn "Activity Detection" off on Fit from within your phone. If you leave that on, your phone will track movement. This seems to cause a conflict if you have a wearable.
Second, activate bluetooth on your phone.
Third, after your activity, check your steps in Fit on your watch. Let's say you have "2,000". Next open Fit on your phone. Now, it may not sync right away. You may only see "0" or "100" or something that doesn't quite add up. However, I usually find that if I close the app and open it back up in a few minutes it DID sync.
You may notice during the syncing process that the steps from your phone replaced those on your watch, but they are not lost. It seems that they actually WILL update on the phone after a few mins.
For example.
Before syncing:
-Phone: 0 Steps
-Watch: 2,0000 Steps
While Syncing:
-Phone: 0 Steps
-Watch: 0 Steps
After Syncing:
-Phone: 2,000 Steps
-Watch: 2,000 Steps
This is just how it works in my case, I'm not sure if it applies to everyone. Don't give up though, the functionality does work. However, Google really dropped the ball with making this app user friendly. It took me forever to achieve what I wanted to. Once you do though, it's great.