I keep separate airframe, engine, and prop logs for all our planes because....well....I’m an engineer, so of course I am going to keep those kind of records. I log inspections for each component in each logbook, but the only one that gets the “official” Condition Inspection statement each year is the Airframe log - it only needs to be in one place, and it makes the most sense there. Nothing wrong with make a similar statement in the other books if it makes you feel better, but it doesn’t mean anything legally.
And, BTW, as Scott pointed out, not all experimentals have the same logging requirements - the little jet, even though it is E-AB, has a completely different set of maintenance requirements (it has an “approved” maintenance plan) and the sign offs relate to that plan, not to an annual Condition Inspection.
Paul