First two channels correspond to standard stereo audio (FL and FR). "Default" mapping creates an "Internal Mono Speaker" virtual sink which is the only sink exposed to applications, which maps to the second channel (FR). This is only accurate when no headphones are connected to the headphone port on the controller; both FL and FR are routed as stereo to the headphones when they are connected. RL and RR always correspond to the left and right HD haptic motors, respectively. (You can play music on it for fun, they sound like subwoofers.) However, since the mono sink is the only sink exposed to applications, games that expect to send 4-channel {audio + haptic} data to the controller end up getting downmixed and behaving incredibly weirdly. Even the Pro Audio profile assumes the output device is 2 channels and as such invokes downmixing anyways unless the stream.dont-remix = true property is set on the node. Unfortunately patchbays like Helvum additionally only show the game as outputting two-channel audio because downmixing is automatic and happens before port assignment; this leads to further confusion.
