Which false generalization does «لَيْسَتْ بَيْنَهُمَا نِسْبَةٌ» prevent?

Al-Murakkabāt — Compound Numerals, the Twelve Exception and Declining Baalbek

• Calling eleven indeclinable
• Identifying Baalbek as a city name
• Treating every two-word phrase as a compound of this chapter
• Treating twelve’s first part as declinable