There's one of those pesky little facts.
"they don't quite share 100% of the same DNA..."
Identical twins DO share 100% of the same dna, fact.
I have second cousins, twice removed, who are identical twins. Their parents claimed that they didn't know if they were identical or not so I gave them two MyHeritage DNA test kits. They came back as 99.9% identical DNA. The MyHeritage people thought that both were for the same person (I guess they never heard of identical twins).
The father of those twins is a twin himself but clearly a fraternal twin--he and his brother do not closely resemble each other.