Regarding multiple peaks per year: To be frank - since we're talking about the general public and not olympic hopefuls - a runner who consistently grows their aerobic plant and judiciously uses races themselves to sharpen will, YEAR-ROUND, be beyond the reach of all of his or her comparably talented but speedwork-happy, peaking-tapering competitors. And the gap will continue to grow year after year.
A side point: I think Hadd, for one, did service in noting how "T" workouts, if used prematurely (i.e., before substantial aerobic development is established), are counterproductive. I and a couple of friends followed DRF several years ago as a bible and began to learn about this the hard way. To be fair, similar mistakes can be made following Lydiard (e.g., with 3/4 effort runs).
I would argue that Daniels wrote his book for the public at large; a group that would probably be willing to have two peaks seasons in a year. That's why he even showed how to shorten the schedules to fit one's racing. And even more importantly in this "I want it now" society, many runners don't want to spend time in base training although we all know how important it is. Think about it. When you go check out someone's running schedule, we all look at the speedwork first.
Lyiard aimed more for the single big peak, such as the Olympics. Of course, back when Lyiard was writing his books and really into coaching, there wasn't the proliferation of road races like there are today.
I probably should be corrected on this, so how did Lyiard account for multiple peaks, such as XC and track, or a road racing season for the spring and fall?