I’m on the team of following General Base most of the time. Unless you’re spending enough hours training at low intensity, you’ll almost always be better served with some intensity.
Base training doesn’t have to stay below Threshold. As @mwglow15 said, it pretty much all builds aerobic fitness, and it’s not likely that you’ll completely lose all of your base aerobic fitness during your offseason. It’s more likely that you’ll lose your top-end punch first.
If you have the time to feed your body lots and lots of easy riding stimulus, you could go that route. If you don’t, you should replace some of that volume with intensity, or you’ll likely start to go backward during the offseason. The workouts we prescribe in General Base are unique to Base training and usually aren’t the same as the ones in Build or Specialty phases, so they’re designed to promote the building of strong aerobic function.
Traditional base isn’t the best way forward for 99% of athletes, and I think if we had a better view of what even the pros were doing, we’d see changes happening there as well. 
I think I remember Neal Henderson saying something about how we don’t build tall buildings with giant bases like the pyramids anymore, and how we can build skyscrapers much taller and narrower by using modern construction techniques and burying bigger foundations in the ground. He was referring to base training and how more well-rounded types of stress signals can build aerobic fitness much better and more quickly than just using tons of easy volume.
Maybe I’m a sucker for metaphors, but it stuck with me. 