Why do heralds worry about name spellings when words were spelled many different ways in the Middle Ages?
The straightforward explanation is simple: while names were spelled many different ways in the Middle Ages, that doesn’t mean that they didn’t follow a set of spelling rules. The rules were just a little different than they are today. So, if a spelling variant follows rules that were used in that culture before 1600, that spelling can be registered. If it doesn’t, even if it’s perfectly fine today, it can’t be registered. That’s because some languages — Gaelic and Turkish, for example — radically reformed their spelling in the twentieth century.