"why would a runner use a beta-blocker as a PED? You need the jitters"
This is a typical example of doping exercised for ignorance. If I want that a runner can run SLOWER, I can give a beta blocker, that doesn't allow the heart to work at its higher level, reducing the transport of Oxygen ad the level of working of the body.
The fact is that Kenyan doping includes the use of a lot of substances that doesn't produce any benefit for the performance, and some time REDUCE the performance itself.
In many cases, this is VOLUNTARY doping, also if the final drug is useless. In this case, is fair to give a period of ban, because the INTENTION of the athlete was, in any case, to look for some unfair aid.
But in several other cases the assumption of illegal drugs is absolutely casual, because the most part of drugs in Kenya comes from Asian Countries that don't have the must (Like in Europe and US) to detail the components on the container. Almost all those drugs, and mostly supplements coming from Asia, contains some steroid, in small quantity, because their final destination is for the gyms, and people frequenting gyms wants to increase their muscles without the limitations and the rules that every official sport discipline has about doping.
I can say that more than 50% of doped Kenyan athletes are not aware of what they take, and act individually without asking advices to some good doctor or their coach (supposing the coach can have experience, but in any case if honest can find the answers to the question).