Are there different profiles of ARCA rails?

Do different ARCA rail manufactures have different edge-profiles on the ARCA rail? For example, would I need brand-specific ARCA rails & adapters or is ARCA a universal measurement where I can take Company A's ARCA rail and mate it with Company B's bipod.

The reason I ask is that I ordered a Mcmillan with an ARCA rail, but noticed in a post (a few weeks ago) that someone's ARCA mount wasn't aligning with the owner's ARCA rail (I speculate that this mount was just defective).

Sorry for dumb question