I have read many, many forum posts here and elsewhere with similar issues to what I'm seeing. Here is an example of one:

https://honda-tech.com/forums/honda-...-work-2664504/

In every other case I've read, the driver side heat doesn't work, but the passenger and rear heat works fine. That is similar to what I'm experiencing, with one exception. I live in MN and this time of year the temps outside are typically well below 20F. So I usually remote start my Odyssey for 5-8 mins before actually getting in. If it's parked in my garage that is more than enough time for the engine temperature to get well above the "C" on the instrument panel, but I will feel cold air coming out of the driver side vent. I don't have a lot of data points, but on at least 1 occasion I had a passenger who said the air on their side was indeed hot right away. Once I start actually driving the vehicle the air coming out of my vent will start to get warmer, eventually, after 5-10 mins, getting hot. The other interesting thing is that if in that first 5-10 mins of driving, if I come to a stop at a light or stop sign, the air coming out of the driver vent starts to cool noticeably and quickly. As soon as I step on the gas and start moving again the temp immediately starts rising again. Usually after 10-15 mins of driving I don't experience the cooling air out of the driver side vent when I slow to a stop. Considering my commute to/from work is about 12mins, I typically don't have much heat while I'm driving.

In all other posts I've read the problem is a heater core. I'm not sure if that necessarily explains my problem since I get heat eventually, but its not until after putting the vehicle in motion.