Sharing my timeline incase if it helps to anyone.
First adult passport after naturalisation:
Application submitted: 23 Feb 2022
Idenitity confirmed: 24 Feb 2022
Document sent: 24 Feb 2022 (via Royal Mail Special Delivery)
Document delivered: N/A (Note: Royal mail tracker shows it’s still at Warrington mail center. However I called RM several times and all the advisor confirmed that the document was delivered on 25th but due to shear volume of Parcel delivered they couldn’t scan each item. Not sure how true is that!!)
Document received by HMPO: 14 Mar 2022
Application processing: N/A
Application approved: 18 Mar 2022
Passport printed: 26 Mar 2022
Passport received: 29 Mar 2022