Personally I don't really like ignoring canon sources/lore and even if my sheets are fanfic, I'd like to keep them in line with the canon material as much as possible. I mean I do sometimes forget or just misunderstand some lore bits so I mess stuff up in my sheets so can't really say they're entirely in line with canon lore, but still I'd rather not ignore any canon stuff. I mean the way I see it, the whole magic of these sheets is making your favorite/interesting historical/myth figures into Servants using template and lore rules presented by the canon so ignoring canon stuff whenever is ehh for me.