Let me try to address your "SPECIFIC" question.
In one of Renato's philosophical threads, he defines SPECIFIC as "all the Training including speeds between 95 and 105% of the speed of the race".
An example of progression might be, at first running the speed in intervals, and over time, working towards something like a time trial.
For a good runner, a workout of 1 hour run at 3:15/km pace, would be considered differently depending on your event: "speed for Marathon, specific for HM, special for 10000m, aerobic support for steeple and 5000m, general for 1500 and 800"
With this philosophy, you can see why long runs are considered so "disconnected" to short events like 800m/1500m, that they provide general support, but not "SPECIAL", or "SPECIFIC" support.
At least that's how I understand it when I'm talking about it here. Lydiard's time trials and development races can be considered SPECIFIC in that sense, while something like windsprints and long runs cannot, because they do not simulate race conditions.
Generic training can be defined many ways but one is that is distant from the race pace, (faster or slower from the race pace).
Specific training can be empirical defined by the one that related to the pace, is closer to the race pace.
Any condition training will produce physiological changes and performance improvement in one unfit runner. But since it´s introduced generic training conditioning, and delays for an extend period than the required, the necessary, and the main training continues to emphasised the type of generic training almost exclusively, the runner will not leave this state and therefore, will not greatly enhance their performances. Eventually the athlete will reach a stage where conditioning cannot be further improved. It´s the right time to start to introduce the specific training variant, progressively, from quality to intensity, in an extensive process to improve the strength endurance factor.
This training style doesn´t happens in the Lydiard training. He does a quite fixed aerobic load, by fix fixed mileage and limit the intensity.
Of course that would be nonsense to read in my write that I don´t care about the volume, or the aerobic condition, and that all training shall be constantly specific.
It´s the moment when the specific training shall be introduced, and not later, independently how far is the peak run.
Specific training can be defined as the stimulus that produces direct improvement in performance capacity. Of course that the format of the specific training depends from another two elements: the target distance event and the training individualization.
Loads must be progressive – or else further overload will not occur or be not effective as should be.
This doesn´t happens in the Lydiard training either, where the load isn´t progressive. An incomplete example but the way you might understand. 1 month before the 74 European champs Pekka Vasala does 1Xmile timetrial, and some days after does 15X400m and the very next workout is 20X200m. This sequence from mile > 400m >200m should be upside down to respect teh rule of progressivity. 20X200m earlier on, 14X400m next and 1mile should be the last one of the 3. Then, on the very next day – and during the period that should be of high level of specificity – he does a 2hours long run ! Why such Lydiard sequence of specifics ? Because Lydiard sees the training order/sequence from aerobic to anaerobic, when he should see from generic to (less) specific, to (more) specific, to top specific or super specific.
The speed-intensity-fast pace decreases (quality) the slow-aerobic pace (quantity) increases the way both approach both do approach to the specific pace in a extensive and progressive process.
The sequence of specific workouts in the modern methodology does follow one deep logic of structure.
I don´t know if it´s inappropriate to quote Lydiard as I did with Malmo. But Renato did post so many times about this issue, how specific interval are done in progressive style: it deals with pace management, the number of sets, the distance of each set and the interval recovery. I don´t see this kind of progressive workouts in the Lydiard training.