While that’s true the article mentions that the definition of “hours with sunlight” they are using is when more than 120w per m2 hits the earth. Around where I grew up the sun would rise around 10AM and then set around 2PM. Not nearly enough to meet power demands.
It is rare but not unheard of to have 0 hours of sun in December[1].
1. Article is in Swedish: https://www.expressen.se/nyheter/morkaste-manaden-i-mannamin...