Поскольку это приписанная строка, вам следует выполнить локализацию из кода.
Objective-C
NSString *title = NSLocalizedString(@"refresh control title", @"comment");
NSDictionary *attributes = @{NSFontAttributeName: [UIFont systemFontOfSize:14],
NSForegroundColorAttributeName: [UIColor blackColor]};
[refreshControl setAttributedTitle:[[NSAttributedString alloc] initWithString:title attributes:attributes]];
Swift
let title = NSLocalizedString("refresh control title", comment: "comment")
let attributes: [NSAttributedString.Key: Any] = [.font: UIFont.systemFont(ofSize: 14),
.foregroundColor: UIColor.black]
refreshControl?.attributedTitle = NSAttributedString(string: title, attributes: attributes)