I never heard of an OTA channel 1 or 37, but many cable systems have them. So I checked with RabbitEars.Info, but I couldn't find an OTA virtual channel 1 or 37 there either. Still, there's no reason you couldn't have, say, a channel 1.1 if you wanted. It could be just a low-bandwidth subchannel of an ordinary station in the area (like many weather channels), and it would make sense to broadcast one of the old "slow-scroll" channel guides there.
It's just that legacy OTA stations set their virtual channel to their old analog channel, and new ones set it to their physical channel number if it's available, and if unavailable they make a "closed loop" with the station with their physical channel number. (For instance, in DFW, after the DTV transition we ended up with legacy channels 21 on RF 29 and 29 on RF 30, so when a new station went on the air on RF 21, it became channel 30, closing the loop.) Since no one was on channel 1 before, no one ever ends up using that channel number now.
(Trivia: some cable systems have a physical channel 1! It follows channel 4, and they move channels 5 & 6 up by 2 MHz to make room. This cuts a couple MHz off of the 20 MHz-wide FM band, but these cable systems usually take that over for physical channels 95-97 anyway. I don't know if the iView has a way to tune physical channels 1, 5, and 6 on these systems.)
Most of the quirks I found in the new 1603 firmware aren't present in the 1511 firmware iView posted on their 3500 firmware page, so that's the version I finally went with. My System / Information page now incorrectly reads Model: iView 3500STBII, and the new 12-hour time format isn't quite right, but I can live with that.
BTW, I think if you enter a non-existent channel number, it's probably a mistake; not an attempt to change subchannels. So while the iView's trick is neat, it probably isn't what you were trying to do. So if I enter a "3," the old behavior of just reporting "Invalid Channel" probably makes more sense than going to channel whatever-3.