UC- Contact Doctor Permission

Hello,

I have ill health including a cancer diagnosis and have just recently made an application for UC and received a message to say:-

'We have tried to contact you regarding your health condition.
To give you the right support, it would be helpful for us to contact your doctor.
Call us if you are happy for us to contact your doctor.
If we do not hear from you, we will assess your condition without any additional information from your doctor.
This may affect what you will be paid.'

Do you know what they need to contact my doctor about?
Is it to verify my cancer diagnosis on my fit note?

I opted out for my doctor to be contacted.
Do you advise otherwise?

Thank you.