An operating agreement allowing (or, more likely, not prohibiting) disproportionate distributions is very different than an OA providing for a special allocation of some sort.
My statement above was referencing the former, not the latter.
OK, what if OA says something on this order?:
Each unit of membership has the same rights, as follows:
Distributions in proportion to ownership percentage;
By decision of a majority of the members, any other amount or manner of distributions may be approved.