You know one often under looked factor other than the esters, is injection location Internally. If you pass through a poke near blood vessels/capillaries and saturate even a small amount of hormone into the blood stream, you may experience the effects sooner. Getting the itching throat/cough post inj is a sign of this. Even if maximal effects take place weeks later, the initial effects by many can be reported fairly quickly, even with longer esters.
Is it the placebo effect? I really don't think so always, but I know their are many factors on this. Sometimes Libido only lifts dramatically initially when starting due to your natural testosterone overlapping with synthetic. The moment the synthetic becomes dominant in the body and production is suppressed, the libido crashes shortly after starting test instead of the expected lift. Personally for most I think a dose slightly higher than the avg TRT dose is Ideal for libido.