I think like many varieties of fruit growing in Cal. and U.S.A. there most likely are many varieties of certain fruit but mostly also many copy cat named fruit. Meaning that people get fruit and rename it to different name, seedlings can slightly vary or totally turn to new different variety. So, I think as in White sapote that there are many different name varieties that really are the same. Some young person needs to dna many of these varieties to get things straight.
I've noticed for sure that varieties need 3-5 years of fruiting before you get the true taste of that variety! I don't have any named varieties of loquat except a few one being 'Big Jim' which in first few years of fruited i was ready to pull out. i waited another year to see how fruit was and was excellent the next year. i have a few white fleshed seedlings and they all vary in taste but i have one that has nice tropical taste notes but mid to small size. I imagine if i cluster pruned it would help but finding the time to manage 2.4 acres and get everything done at right time is not that easy!
Sorry to put you on spot Fang, about scions i should have asked first, don't worry about scions!