I say yes. If you have a bad unwrap, then you usually wouldn’t have a good lightmap since getting a good lightmap requires you to unrwrap it well. If you just unwrapped it once for say, the light map, UE4 would take that unwrap and unwrap it again in channel 1 (channel 0 if your texture map) and use that as the light map.
Let’s say you model something and don’t unwrap it at all because that’s the only way this scenario would work. You would get an auto-generated unwrap (channels 0 and 1) and you would get loads of UV overlaps, so the lighting and shading would not look good, thus even if you put a solid color on the model or a chrome material, you would see all the shading lines and it would look bad. SO with that being said, you need at least one good unwrap and roll the dice that UE4 will unwrap a second light map channel that looks good.