Seasonal/fresh are essentially the same thing. Only thing that is really required for fresh is that it’s new servers with it not being possible to move progress from other (non fresh) servers over to it.
How characters are handled after would not be a determiner in whether ppl consider it fresh or impact how much ppl are interesting in playing very much but the most standard route used in other games is letting there be a one way transfer from seasonal -> permanent servers.
The only thing kind of iffy about that in classic WoW is something dumb like letting more people have the AQ mount in permanent servers.