Same watch here. Even before Pie, mine never showed on the Bluetooth icon at the top that it was currently connected. Even in the Bluetooth settings it didn't show as being currently connected. Only in the Wear app did it show connectivity. Same behaviors now with Pie.
I saw a video about fixing Android system issuse, it says to fix OTA Update Failure for Samsung Galaxy phone. Maybe helpful with you.
The app says I'm connected, my phone shows it is paired but not connected.
My 2019 Mercedes-Benz AMG E 63 S 4MATIC Sedan is also having Bluetooth issues. I'm going to have the dealer send someone out today to check it. I will let you know if it is on their end.