SSDI approved in 2024, incorrect form?

My husband applied for SSDI in September 2023.  After over a year, in October 2024 it was approved and he received a lump backpay.  The letter said he was approved/eligible for SSDI as of December 2023.

The SSA letter from October 2024 says his benefit for December 2023 was $2,580.  The rest of his lump backpay was for 2024 up until that October approval.

 

Looking at his SSA-1099 form as I am doing taxes, it says that all of his benefits were for 2024.  Shouldn't a portion have been for lump sum back pay for 2023 to include the December 2023? 

Why doesn't his SSA-1099 form indicate a lump pay for 2023?  Is there a way to have this verified?  Does it matter?  Does it impact our taxes that much?  (As his spouse, I do work and together our income will be taxable, including his disability benefits).