And the information should be provided to the players - whether they are identical or not.
If there is already experience in programming client-server communication, then technically all this is quite simple.
So, since creating such protection would be not difficult, the actual motives of the Heroes team for disabling plugins were (as usual) much less noble than it might seem to naive players. The Heroes team simply believes that it has the right to profit from the legacy of NWC (pardon, to develop it), while other modders do not have the right to profit from Heroes.