If an enchanter casts hold person this feature lets it hit two targets if it normally targets 1?

Split enchantment question. If an enchanter casts hold person this feature lets it hit two targets if it normally targets 1But let's say you use a higher spell a lot to increase the amount of targets up 1. Does that mean you only get 2 targets again?

— Maia Cursed (@TheCrossDM) October 4, 2017

Split Enchantment works only on a spell that targets one creature when you cast it. #DnD https://t.co/Cg7R9Ugeo4

— Jeremy Crawford (@JeremyECrawford) October 4, 2017