I don't think equivalencies are that smart...they have same completion status and likely will show your training hours twice but it depends on how you track it. IF it’s only via attendance on the course that actually attended, I don't think you will see a doubling of the session times; only if you use something like the CPE (CE credits) fields on the courses.

You can test this easily to see the effects on reports.

@Akto as @lrnlab mentioned, equivalencies today have a few options to choose from.
In most cases, mapping 1 to 1 (or many), but the completion tracking across all courses the same. Complete course A, and B is mapped as equivalent, A and B are completed. Vice versa.

Here are some of the potential selections you could make depending on your use case:

For CEU’s, marked on the Course shell or Properties level, they should be add up in this scenario inside Custom Reports (to 14). Each course will have it’s own enrollment and completion record in the end, contributing to whatever CEU/score allocation you may have set inside Course Properties > Score & Credits > Credit value (CEU).