@Shammi In case it helps clarify: It’s perfectly allowed to assign someone who is a circle’s Rep Link to its Lead Link role; it’s just not allowed to elect someone who is Lead Link into the Rep Link role. The prohibition isn’t on the same person filling both roles - there’s nothing wrong with that; the prohibition is on the assignment/election into the role, and only in one of those two cases.
The Lead Link's purpose is to hold and represent the interest of the parent circle INTO the sub-circle. The Rep Link's purpose is to hold the tensions OUT of the sub-circle into the parent circle. The reason a Lead Link can not be elected as its Rep Link is the two roles can conflict and one person can't reasonably process those tensions if they fill both roles. Basically, it creates a conflict of interest.