The source lists special cases where an intended stay does not create legal residence, including:
• 2 towns when the person does not designate one as the place of nightly residence;
• open wilderness for someone who is not from the tent-dwelling category addressed by the text;
• a Muslim army in enemy territory;
• an army in Muslim territory while actively besieging armed rebels.
These are technical classical cases. They should not be replaced with the simplistic rule that 15 calendar days anywhere always ends travel status.