But that is a new credit card application form, so I'd expect them to require the information. For an existing card I have made on-time payments for years, that's all they need to know.
Here is an article (from 2018) explains about the very same credit card scam as is happening to you, @Tom Young . It explains that the scammers pretend to be from the legitimate credit card company, and then require you to update your information either in writing or online. Even though the phone numbers and website look legitimate, the people you are talking to when you call the number are not really from any credit card company. The article also goes into several other scams that are being used with reference to credit cards. https://www.thebalance.com/5-credit-card-scams-to-watch-out-for-4083118
Not a scam. I asked for an increase in my $15,000 limit, to buy a $26,000 car, and get the 1% bonus on the amount. https://www.creditcards.com/credit-card-news/credit-card-company-asking-for-my-income.php
Well... that's different. From your original post, it seemed that the credit card company (or someone) wanted your information out of the blue. I'm not surprised that they want your updated information for a sizeable credit limit increase.