Italian 258 does have a real name out there somewhere. In the US the situation is very convoluted because of the way all of the different varieties were brought here. Italian 258 is popular because many growers have trialed it over long periods and had success. There was absolutely no marketing involved in the name Italian 258, the name was lost. The Paradisio's have different names because they carried them from the old country still attached, presumably different regions of Italy have their own idea of what paradise is ;)

Funny you mention the Mt. Etnas because my question about planting arrangement is related to my own trials of them. There is quite a bit of variation from tree to tree every year, even branch to branch in some cases. 

 

All of the Etna fruits above came from plants with the same mother, they have varying levels of winter damage and therefore different growth rates so even though they are the same age and planted right next to one another they fruit sooner or later than each other, have necks or don't, thin peels or thick, darker or lighter etc. Take a good long gander. Of course there is argument!

I had a chef taste several different Etna types and she picked up very subtle differences between them and I do too but only sometimes, some have slight leaf shape differences that seem to be consistent and are more apparent, like Sal's and MBVS for example. If I do go through with the trial I may just keep the results to myself, since some people will be dissapointed however it turns out. I saw a plant on eBay being sold as a "must have" with an obscure name from a simple list that had no authoratative information from a relaible source for the buyer to ever verify they have been sold the correct variety, it has an Etna leaf but the seller neither declared that or showed pictures of fruit or the mother. So yes you are right it is confusing and some people could be quite genuine while others take advantage.

I have a small fleet of RdBs in various situations and have seen more variation than you have between the 2 "varieties". At least with Bayernfeige there is a claim made, it is supposed to be more cold hardy than the usual English Brown Turkey. Well, how a patent office could verify that I don't know, but you could easily fake a hardiness trial by selecting trees that are more hardened or softer. In Lubera's situation they make no claims, so nothing to confirm or deny.