Moderator: United Airlines
Join Date: Jun 2007
Location: SFO
Programs: UA LT Plat 2MM, Hyatt Discoverist, Marriott Plat/LT Gold, Hilton Silver, IHG Plat
Posts: 67,066
It appears you may have been two boundary cases.
1) On travel crediting to UA? but using another *A status to enter UC
2) Using a virtual TK *G card
The rules on 1) are a bit vague and while it will work most of the time, you should expect an occasional issue.
For 2), even with UA doing this for 2018, there will be a transition period for agents to get use to this.
So, while you may have not been doing anything wrong, you need to be realistic and expect a few odd looks / questions. You are not traveling in a standard way.
And don't bother call TK, the UC agents are not going take the word of an unknown voice on the phone. Rather they will do what they did, and research it via the tools they have available. One should expect such when using these tricks / travel hacks.