I want to say that it probably doesn't cause it exactly, at least not in the way that it would become an ongoing medical problem if the fluid amounts were lessened or stopped. But I don't really know that for sure. It is possible to have too much sub-q fluid such that the cat gets over hydrated, loses too much potassium, etc.
One thing I know is that treating with sub-q fluid can reveal and temporarily worsen a problem that before was too small to notice easily. For example, when my cat started sub-q fluid treatment she had some trouble and eventually we discovered she had congestive heart failure.
This doesn't mean you shouldn't treat with sub-q when it is warranted, but it is something to look out for when starting treatment.