it may be a bad rule....but it helps prevent the problem of teams taking advantage of a team out of contention and aquiring an impact player at a time of year when trades shouldn't be allowed anyway....
Great overall discussion.Wouldn't what you have stated here be covered and governed by the league's trade deadline? Honest question.
As with any actual professional sport, it is very common that the haves do a fair amount of business with the have nots the weeks immediately prior to the deadline.
The bad teams sell of their most marketable assets, developed players, and plan for the future, undeveloped talent or draft picks. The bad teams can maximize the value of their only commodities at that time. (Time defined as the moment a good team realizes it can win now and the trade deadeline is within one week, while the bad team realizes it needs to look ahead and has one week to act.) The good teams do everything necessary to win now, while mortgaging their future and operate under terms and conditions set forth by the weaker teams in most instances.
It is a natural series of checks and balances and the type of transaction that drives a dynasty league. This rule blocks the conduit between the two sides at the most opportune time for the two to do business.
The easiest way to allow for this type of commerce to exist and to eliminate a so called "firesale" scenario would have to be to institute a very early trade deadline.
As the rule is stated, though, that is not addressed. As it is written, that rule would make it very hard for a bad team to rebound.