To answer your question, No - you are not correct. I do not believe there is a single other case in the forums of not getting premium channels on TWC and it not being TWC's fault. All the other discussions are of a different sort or are not Time-Warner related. Your problem is a simpler one than most. Time Warner has the legal responsibility to get it working. If you want to reward them for their illegal actions by getting their DVR, you can do so.
Time Warner has a national CableCard line 866-606-5889 that is often helpful as opposed to a local installer (my Time-Warner installer insisted that the TiVo itself was the "tuning adapter" I was talking about, and that Time-Warner furnished no such items - I went down to the Time-Warner store the next day and installed my two tuning adapters myself.)
TiVo Roamio:Felix TiVo Premiere:Bob TiVo XL4:Fred TiVo HDXL:Sharon TiVoHD:Susan