LIghtroom is totally non-destructive in editing, so there is no change in resolution when you edit photos or videos.
If you change the video there will be some loss of resolution. You decode a lossy compressed video, change it (eg color) and encode it back into a lossy format (eg avc). In most cases the decrease of quality should not be noticeable.
But compression isn't loss of resolution, its loss of quality, these two are not the same.
I agree that there is a loss of quality after exporting, but I do not agree that there is a loss of resolution.