Sam Bee
TVWBB All-Star
If you compare LP to NG schematics on weber.com the burners have different numbers. Just a quick search picking two random grills I found these part numbers:
Genesis EP-310 LP Black (2011-2012): 62752 - LP Burner Tube Set, Genesis '11
Genesis EP-310 NG Black (2011-2012): 62799 - NG Burner Tube Set, Genesis '11
Spirit II E-310 LP (2017): 67025 - LP Burner Kit, Spirit II 3 burner
Spirit II E-310 NG (2017): 67103 - NG Burner Kit, Spirit II 3 burner
Why would they be labeled different if they're the exact same? If you compare other LP to NG parts they will have different part numbers if the part is different. Like for the previous versions of the Spirit and Genesis models where the tank went inside the cabinet, the bottom panel has different numbers because they're different parts. The LP versions had a hole in the bottom panel for the LP tank. For the NG models, the bottom panel doesn't contain that same hole for the propane tank, obviously. Instead it is solid all the way. But for an item like the flavorizer bars, grates, side tables, lid, etc., there are no distinctions between LP and NG because they're the same no matter which type of gas you're using.
Edit: I looked up schematics for a Genesis 3000 and the burners are the same item number. Maybe the different tubes based on fuel choice is a newer thing?
Yup, it looks like those part numbers you listed are for the newer grills. The old school grills (x000, Silver B/C) have the same burners (within the model family e.g. burners for a genny 1000 won't work in a silver b and vice versa) whether it be LP or Nat. gas.