VT, if, as you say, you have no supplemental heat, then the installer was able to save a few dollars by installing a "single stage" tstat. As you dedueced, this stat has the ability to work a switchover valve (O&B) but no supplemental heat (W2, or X).
The real problem here is the lack of uniformity between manufacturers. For instance, some manufacturers use E for supplemental heat, some use X and some use W2 or W3. Trane actually uses (or used to use) several of these. As you also figured out, some manufacturers default to heat and switch to cool (O) and some manufacturers default to cool and switch to heat (B).
Now, for a fundemental understanding, the thermostat is just a switch. What it switches is determined by what you connect to it, and in what sequence or order. IFF you wanted supplemental heat from your existing stat, connect the wire that controls supplemental heat to the W terminal. But, you'd have to disconnect it each spring, because when Y energizes in cooling, it will close the supplemental heat switch also.
If you want, you can use the switches in your thermostat to switch the TV on and off. It's just dry contacts.
But, it sounds as if you have a pretty good handle on the situation at this time. I hope I haven't confused the issue.
There are no stupid questions. . .just a lot of inquisitive idiots.