Chat agent asking my SSN and DOB

I just had a chat with Xfinity agent to get confirmed on ongoing promotion.

I only asked if two promotions can be applied together: (1) $500 device credit for 24 months for purchase of samsung S23 ultra device without trade-in upon porting in from another mobile company, and (2) $20/mo discount for 24 months on Xfinity home internet service with unlimited mobile plan. I got confirmed that these two promotions are applied together.

Then I asked if the device will be delivered to my address or if I can choose to pick it up at a local store. The agent answered that device will be delivered.

And then, the agent suddenly asks my SSN and DOB. I refused giving it on chat, and the agent asks these information again through suspicious external link, staring with 

http://iguard-po-1pp.slb.comcast.com:

I refused to give delicate information and closed the chat. However I feel it is strange that the agent request such information for a purpose that I did not asked for.

The agent said "For checking the number of lines eligible and to create your mobile account profile I'm sharing an secure form in which I request you to please enter your SSN and Date of birth and submit the form"

The agent also emphasized "your personalized secure data link:" with bold font. Is this online form truly belong to Xfinity system and Xfinity asks SSN and DOB on chat for a purpose of the customer did not ask?