There's no need to overstate. It's as simple as this.

I say to you, "You can only have 1 active quest at a time."

Do you then think:

A. "I can have 1 quest active at a time, so once I finish it I can pick up a new quest."

B. "I can have 1 quest active at a time, so once I finish it I must wait for some undisclosed timer to run out before I can pick up a new quest."

If you are picking "B" I'm not sure where you learned English, but it probably isn't the same place as me (or the OP). Knowing that leves are on a timer ahead of time is great, but it doesn't mean the NPC should assume you know that. Once you complete and turn in a Local Leve it is removed from your log and thus you "don't have it" any longer. It's not as clear as Regionals which you do retain in your log.