In 25 years in Spain, insuring cars and motorcycles, I have never been required to name anyone else who would drive. The policies have always covered all drivers. Albeit that conditions may apply to say, younger or less experienced drivers than me.
I recently confirmed that my wife was covered on my policy.
This was the reply:-
Thank you for your e-mail. Your Seat Ibiza is covered for driving by any person 25 years of age and over with at least 2 years valid driving licence. The vehicle is covered on a Comprehensive basis even when persons other than yourself are driving, so long as they comply with the above.