Correct but can we presume that the LFE content is, in fact, duplicated in the main channels or if it is, literally, the bearer of low frequency effects? Of the three options in this poll, I can and will do any, depending on the recording.The AVR's output to the subwoofer has two mixed contents:
1) The LFE channel that is the .1 content channel. This channel can be empty or silence the same way the Center channel is silenced in a Quad mix.
2) The Bass Management content. When a speaker (other than the SUB) is configured as "Small", the frequencies below the crossover (normally 80 Hz but can be configured to other frequency) is sent to the Subwoofer instead of the speaker channel. Otherwise, speaker configured as "Large" receives the full channel band and nothing is sent to the Subwoofer.
Some recommend that all speakers be configured as "Small" even if they are good full bandwith speakers, because the Subwoofer (powered) will be more capable of reproducing the low frequencies. And the main speakers will be working better and cleaner with less load.
Some others prefer to have full bass from all main speakers if they are capable of low bass.
The music with very low frequency (organ, electronic synthesized,...) can be properly played through Bass Management to the Subwoofer. There is no need to add content to the LFE channel, that could be phase delayed, thus generating room cancelation problems.
But if someone has speakers not capable of low frequencies and the Bass Management is not properly configured, then he will miss the low frequencies. For that people, I think, some producers keep generating content for the LFE channel.