Sayyiduna al-Fadl (may Allah be pleased with him) said: I departed from Arafat with the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) kept saying the Talbiyah until he stoned Jamrat al-Aqabah; he (peace and blessings be upon him) said the Takbir with each pebble. Then he ended the Talbiyah with the last pebble.
(b) The Shaykh (may Allah have mercy on him) said: His saying the Takbir with each pebble indicates that he ended the Talbiyah with the first pebble, as we have narrated in the hadith of Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him); and his words "he kept saying the Talbiyah" until he stoned the Jamrah mean: "until he began stoning the Jamrah."
As for the addition in the narration of Sayyiduna al-Fadl bin Abbas (may Allah be pleased with him), it is gharib (unusual).
The Shaykh (may Allah have mercy on him) said: Saying the Takbir with each pebble indicates that the Talbiyah was ended at the very first pebble, as is clear from the hadith; but the additional words at the end of the other narration are indeed unusual.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9604