Molecule inside molecule

[umardev500]

In Atomic Design molecule is a collection of one or more atoms
but whay I see the Modal Molecule inclue ButtonIcon Molecule

here is the link of code:
Modal: https://github.com/diegohaz/arc/blob/master/src-example/components/molecules/Modal/index.js
ButtonIvon: https://github.com/diegohaz/arc/blob/master/src-example/components/molecules/IconButton/index.js

so does molecule inside molecule is true way?