Perhaps the issue is that many (most?) middle distance runners don’t truly periodise to maximise their track performance. Maybe that is the biggest impact a CFTS philosophy can have.
It appears they (by this I mean many / most) don’t have a GPP, SPP, Competition setup they have summer (track) and winter (Xcountry and road racing). Certainly it appears speed development is not in place all year. From what I have read lately many don’t use any sort of high / low set up. A recovery day may be 2 a day runs of 45 minutes or a 75 minute run.
Lets take a hypotheical situation. The track season finished 4 weeks ago and you are a national level 800 / 1500m runner whose goal is to get to Beijing in August next year but still have a way to go to achieve the qualifying standard. You usually run Xcountry and road in winter, because well that’s what you do (no other reason). Speed development has been negligible in your training.
You could use Fall / early winter for GPP then do some road races over 5-10k as SPP than another GPP in Spring including some 200m & 400m races building to the critical races post Christmas? Speed development would be throughout as per CFTS.
What about weights? Do you see that as a part of the training of a middle distance runner?