Why can نَدْمَانٌ not be classified merely from its ending?

Cause of Ghayr Munsarif: Additional Alif and Nun

• Because its feminine نَدْمَانَةٌ is on فَعْلَانَةٌ
• Because it has no alif
• Because it is always a proper name
• Because every adjective is declinable