Makes no sense to me ~ every car I have ever owned (including a Mk3 Golf VR6) I have always checked the oil when cold and on flat ground.
You're trying to access how much oil is in the engine after all so imo you need to leave it overnight for as much of the oil as possible to drain through back to the sump which is where you are reading the level from.
If the engine has not been turned off long ago then there will still be oil trapped around the engine in galleries and on components. Giving you a less than true reading imo.
isnt that the point
if your checking it full and its ok then once it circulated drops below minimum and starves youve got an issue
if you check it after its been turned over and oil pressure is built if its above the level you no its safe as it wont be below that level,
every mechanic ive known when doing an oil change will top it up with oil check it start it for 20-30 seconds then check it to make sure during operations its not below the minimum level