Is the two-rak'ah prayer mentioned in the hadith "Whoever prays Fajr in congregation, then sits remembering Allah... until his saying: complete" an absolute supererogatory prayer or Duha prayer, and does it take place 15 minutes after sunrise?

The Hadith (definition) states: "Whoever prays Fajr in congregation, then sits remembering Allah until the sun rises, then prays two rak'ahs, will have a reward like that of a complete Hajj and 'Umrah (definition), complete, complete, complete." This Hadith was graded hasan (definition) by Tirmidhi. These two rak'ahs are the Duha prayer, and they are called the Ishraq prayer if performed after the sun has risen to the height of a spear and the time of dislike (for prayer) has passed. The Permanent Committee was asked about these two rak'ahs and replied that they are part of the Duha prayer and have a special virtue because they are linked to remaining in the prayer area after the Fajr prayer until the sun rises. The best time for the Duha prayer is when the young camels feel the heat of the sun (i.e., when Duha becomes intense before the sun reaches its zenith). The time for Duha begins after the sun has risen to the height of a spear (approximately 12 to 15 minutes after sunrise) until just before Zawwal (midday).