Surround output is under the control of the film director. It could be wham-bang battleground effects, nighttime ambience (crickets), or nothing. One of my favorite films is strictly ambience surround. At first you might think that there is no surround, but if you disable the surrounds, the whole film collapses. This film should not be the user’s first surround experience because new to surround listeners expect to be smacked in the back of the head by surround effects. We’ve been through this before. Early stereo orchestra recordings often isolated left and right with a dense curtain. It was obvious stereo, but not very natural sounding.
In answer to your question: No, the surround channels would not usually provide full range audio for the kitchen. You could set the TV for stereo audio when you wanted to watch in the kitchen, but I suggest that this would soon become an unwelcome chore.
As a trial I suggest that you add a pair of speakers near your kitchen viewing location and experience the results. Give it a few days to get used to the environment. Some viewers (such as me) will be very annoyed by the latency, while others will welcome it. Sound is rather pokey, traveling at about one foot per millisecond. For live events in a large hall there will be latencies as the sound bounces around. The SONOS latency brings back the large hall live concert experience for some listeners.
In the end only you know what sounds “best” (to you).