Not really that in fact. The fatty acid solution injected using a syringe is made AFTER the entire enema cycle. It is rather a boost given to the body, to help it restore the tightness of the intestinal membrane. It is therefore probably advisable in all cases (should be checked, but I believe that there is no contraindication, since sunflower oil is nothing other than a food as such, highly profitable for the organism).
It would have seemed more logical to me an enema with a water + oil emulsion which would allow safer evacuation than with water only. But as long as it works: why not!
Obviously, in case of serious and / or chronic pathology, it is up to the doctor to say what to do. And if he does not recommend, it may be time to take a second opinion from one of those who encourage this practice (or even above). For he alone, will be able to put the right priorities and define the operating mode adapted to each case. .
Very often those who have recourse to a medium or long duration fast do so because all the other techniques have failed or have proved insufficient or even ineffective and few doctors are used to medium and long duration fasting. 'where all the a priori on this subject and when the fasters do not present the expected pathological characteristics, they emerge the famous discourse of the exception, of "she was lucky", etc ... and on the other hand rise in pinpoints the few failed cases (nothing works 100%!) among fasting "do-it-yourselfers" (such as protest fasts without any preparation).
ps: I have not heard that doctors, even well informed, have recommended a long fast to cure cancer for example (I take this example supposedly extreme because most people consider this "disease" as incurable other than with radiotherapy, drugs or mutilating operations)