One of the things that makes a person suspect as an "annointed" would be if he starts partaking right away after "coming into the truth".
Why this is so, nobody seems to really say - but in the old days post 1975 when there was something of a mini-boom in partakers, we were told to "watch these newly annointed carefully". I guess they liked their new annointed "well seasoned" as Bethel GB wannabees before legitimizing them.
Not scriptural even by JW standards, of course - example might be Apostle Paul; BAM - flash of light on the way to Damascus, and you are IN.