I had a similiar experience with pokernordica,thet wanted copies of my credit card,front n back,which I never used at any merge site,or any
poker sites,because I used usemywallet,for all my business.
I told pokernordica I had no intention of using my credit cards at their site.Recently nordica stopped taking usemywallet and wanted my credit card info again and I refused..so they closed my nordica account.So thats that.I did get my money off nordica beforehand,so its all good.I dont know why nordica stopped using usemywallet....most other merge sites take it.
But,if I had to use a credit card for deposit and withdraws,I can see the need for requesting my info,to stop stolen credit cards from being abused at poker sites....maybe the site pulled your credit history and know what credit cards you have already?