There is the wanted signal and the unwanted signal(s). For simplicity we refer to the latter as noise.
Cross-talk is, by definition, an unwanted signal. A lawful broadcast transmission is an unwanted signal. The radio-frequency signal emitted by a poorly constructed switching PSU is an unwanted signal. The high-frequency "mush" emitted by an old television set -- one that is faulty -- is an unwanted signal. The cumulative sum of all those unwanted signals is the noise.
I cannot see how any one unwanted signal from one source can be responsible for the decrease in another unwanted signal for another totally unrelated source.
I would say that the level of other, non-crosstalk, noise received should be the same, be independent of whether you are getting crosstalk or not.
I also think that level of received non-crosstalk noise should be the same when router receive crosstalk.
I believe, therefore, that I am agreeing with you both.