Bismillahir-Rahmanir-Raheem.
Alhamdulillah, Nahmaduhu was Nusalli Ala Rasoolil-Kareem.
The book ‘Ar-Raheequl- Makhtoum’ (The Sealed Nectar) is a good summary of the Prophet’s Biography ﷺ.
The reason it was awarded by the World Muslim League (Makkah) was because it summarized the Seerah well. However the book has some weak and fabricated narrations.
Even Shaikh Safi-ur-Rehman Mubarakpuri Rahimahullah never claimed that his book is entirely authentic or based only on authentically confirmed reports.
In order to know about the unauthentic narrations in the book ‘The Sealed Nectar’, refer to the following books:
1. Taleeq Ala Ar-Raheeqil-Makhtoum by Shaikh Muhammad bin Abdullah Al-Malaah in Arabic in one volume. In this book the Shaikh mentions some of the weak narrations in the ‘Sealed Nectar’.
2. ‘Ma Sha Wa Lam Yathbut Fis Seerah An-Nabawiyyah’ (Arabic) and translated and summarized into the English language as ‘Famous But Unauthentic Stories From The Seerah of The Prophet Muhammad ﷺ’ (by Mohammed bin Thajammul Hussain Manna).
This book mentions around 110 famous but unauthentic narrations from the Seerah. Some of the fabricated and extremely weak narrations mentioned here are also found in Ar-Raheequl-Makhtoum.
May Allah reward all of us with Khair. Aameen.
Note , the PDF link of the second book:
Famous But Unauthentic Stories From The Seerah of The Prophet Muhammad ﷺ by Shaikh Muhammad bin Abdullah Al-Ushan (translated and summarized into English by Mohammed bin Thajammul Hussain Manna)
https://drive.google.com/file/d/1HuFEroC9t5nwCK4BRWaFMQu_frdFu9hs/view?usp=drivesdk
The First English Seerah Book Only Based On Authentic Hadiths!
Saheehus-Seerah 