Al-Quduri initially describes iʿtikāf as recommended. Later Hanafi treatments distinguish the communal emphasised Sunnah of the last ten days of Ramadan, an obligatory vowed retreat, and general voluntary retreat.
These are explanatory school distinctions, not additional words of the quoted sentence. Their legal consequences should not be treated as identical.
Opening interactive controls...
Bab al-Iʿtikaf: Rules, Restrictions, Invalidation and Vows
Al-Quduri initially describes iʿtikāf as recommended. Later Hanafi treatments distinguish the communal emphasised Sunnah of the last ten days of Ramadan, an obligatory vowed retreat, and general voluntary retreat.
These are explanatory school distinctions, not additional words of the quoted sentence. Their legal consequences should not be treated as identical.