I did understand. The TV has a tuner that can populate the guide for all channels that send the data, including what is on now. Many sub channels do not send this data, so each system or TV handles that however they like.
The Dish OTA tuner does not populate the guide data, nor show what’s on. The Dish box appears to use Local Channel guide info it has from its own guidendata to populate some OTA channels that are the same, but does not populate all channels that do send data. You can confirm that by looking at what you TV gets for OTA data, and what Dish populates into the guide with and see that they are not the same data.
The DISH guide data is there even if you don’t subscribe to the channels. Set you guide to show non-subscribed channels and you will see guide data for them as well. I can only assume that even if you are not subscribed to locals, the Dish box will move some channel data into the local channel’s guide for OTA, but I have not tested that theory.
You can further confirm this by noting that the data your TV gets from OTA is not the same data you see in the Dish guide. There is some OTA data, but not a lot of data being sent OTA for each channel, and the data that gets populated into Dish’s guide is much more detailed, and amazingly (not) matches exactly what they put into their own local channel guide.
Bottom line at this time based on all observations and tests: Dish is not using any OTA guide info to populate the Dish guide. I’m reasonably sure of this.
Lastly, sensitivity of OTA tuners varies greatly. I have two TVs connected to the same roof antenna, and one gets about 10 channels more than the other.
Just in case you are curious why I’m fairly sure about the OTA tuner: Besides the imperial testing of guide data on and off the Hopper box, I was a pioneer in digital television, helped set many standards for cable and satellite digital transmissions, and one of three architects for the basic design of digital set top boxes, much of which is still used today. The compression technology has improved greatly, but transport of shows and data is still fairly close to the early designs and standards. I was also a member of the ATSC (over the air digital signals) standards committee (and one of a few people that rejected the current method for the European DVB standard which would have been so much better),, so I have a good understanding of how OTA signals work, as well as how set top technology gets its guide data.
Sorry for the long winded answer. Hope this explains what you might be seeing.