Formerly engine cleaners were heavily loaded with Caustic Soda (lye) which woiuld be very distructive to any aluminum parts. Modern Al block and head engines have probably required these cleaners be reformulated so they aren't as caustic.

Nevertheless, why do you guys need such heavy duty cleaners for bike parts? Mineral spirits, Simple Green or one of the Citrus based cleaners (d-limonine in another formula) are plenty adequate.