this will confuse also a lot of manager when they try to explain their results.
Personally if I would get 1st league hopefully sometimes, I would not like to see that I have to do TIE agreement with others just because everyone do it. Do that over and over "will you accept to TIE next match with me?" "ok" over and over again, this is so boring.
The point that manager cannot deduce team effort doesnt mean that his match reading will be completely lost. In fact, if he knows something about the game, he could figure out that there could be something messed with others team effort, while he ended up like this.
This doesnt affect the game itself, because you doesnt know opponents effort before game anyway and after-match analysing are complicated anyway.