that is to say that the essential performance defiened in the particular standards may be not the essentail peformance of the device depending on the risk mangagement rusults?
Depending on the device design, in fact.
for example, the accuracy of loading factors ,if the manufacture dose not regard it as essential peroformance through the identifying procedure ,is this compliant with the particular standard ?
It's not a "regard", you have to follow the procedure to evaluate essential performance.
In the case of 203.6.4.3.103, the requirement is (at least in the draft I've got) "For HIGH-VOLTAGE GENERATORS operating with AUTOMATIC INTENSITY CONTROL in RADIOSCOPY, continuous indication of the LOADING FACTORS that vary shall be given at the CONTROL PANEL."
IN this case, if the equipment does not operate with AUTOMATIC INTENSITY CONTROL in RADIOSCOPY (a design feature), it obviously does cannot have this essential performance (meaning, after manufacturer follow the process, it won't include this item).
In the case of 203.6.5 Automatic control system, if the equipment is not for indirect radioscopy, it obviously does cannot have this essential performance (meaning, after manufacturer follow the process, it won't include this item).