To be honest, this is for security purposes to avoid credit card points to be fraudulently used or to be sold.
As a Miles&Smiles member for at least 15-20 years, I never had this issue online, nor any of my relatives ( even with those with different last names ) when we were using miles among us.

I never had personal experience with English speaking outsourced call center agents, however, from what I hear from others that doesn't speak Turkish, the outsourced call centers could be a hit or miss.