A rondo and a baroque ritornello share similarities, particularly in their structural characteristics. The key similarity between the two forms is:
Both forms include a recurring theme.
In a rondo, the main theme (A) alternates with contrasting sections (B, C, etc.). Similarly, in a ritornello, the recurring theme returns between contrasting episodes. This repetition creates a sense of unity and coherence in both forms.
The other statements you provided are not entirely accurate. While both forms may incorporate elements of exposition and development, it's not as clear-cut as in sonata form. Rondo and ritornello forms do not typically feature extended introductions and codas as defining characteristics, and while they can be used in operatic arias, this is not a defining similarity either.