See here for lots of info regarding base:
One other thing to consider is that in most, if not all cases, the plans are designed for people who are time crunched. Arguably the best approach to base would be to go out every day and spend multiple hours in the saddle doing zone 2, but isnt often possible for people juggling a “normal” life.
I’m not sure how plan builder chooses the base workouts but it may be worth looking at individual plans and choosing traditional base instead of sweet spot base, to address some of your concerns.