Hmmm, I believe my Yamaha RX A3050 9.2 has 2 subwoofer outputs. Are you saying the two outputs is only in fact one channel? So what is the .2 in the 9.2? It also has Dolby Atmos so I figured I would use it. Am I mistaken about something?
Yes. It is marketing gimmicky. My previous Onkyo receiver had 2 subwoofer outputs, was labeled "7.2" right on the box, but there is no movie to date that has ever been encoded on to a DVD, blu-ray, or UHD 4K disc that has anything beyond a ".1" mix for the subwoofer channel. The Onkyo simply had 2 subwoofer connections that were internally connected to the same subwoofer processing (both output the exact same). Your Yamaha is doing the same thing.
You get the exact same effect by using a Y-cable splitter and a single subwoofer output as you do using 2. The receiver basically just splits/duplicates the same .1 output to both subwoofer connections.
My current Anthem MRX-1120 even says "11.2" on the packaging and manuals... Even their website says it, but they at least note it as: "Two Sub Out Jacks (parallel)" meaning that both subwoofer outs are getting the same signal. MRX-1120 Overview
In the manual for your Yahama, on page 19 it states about the subwoofer processing:
"Produces LFE (low-frequency effect) channel sounds and reinforces bass parts of other channels.
This channel is counted as “0.1”. You can connect 2 subwoofers to the unit and place them on the left/right (or front/rear) sides of the room." It even admits that it is just ".1" even though you can connect 2 subwoofers.
MARKETING!! All the big players do it.