I have found as many as 20 beetles in a grooved bottom. They bees will get around to filling them sooner or later and you'll find beetles entombed in there when they do. But I have made a habit of filling the grooves on frames that I don't put wax in for brood boxes. I started with pouring wax which works fine but now put strips I cut from scrap in them. The groove/split doesn't have to be completely filled, just enough to allow the bees to reach the beetles is good enough.
A little work up front like frames and boxes, keeping the cracks down so there are no hiding places goes a long way. Keeping excessive comb off the boxes that the bees can't patrol helps as well.
Maybe I'm being nit picky but I'm not loosing hives to them and I'm not treating and being bothered with trapping beetles either.
"Success is not final, failure is not fatal: it is the courage to continue that counts." Winston Churchill