Not with the Bio series apparently, but at least on the Yubikey 4, when you're setup with OpenPGP, a tap works with a single request and it prompts you to tap with a blinking light. If it's blinking when you haven't done anything to prompt a tap, that would be something to worry about. If you do something that prompts a tap and a malicious process also requests something from the key at the same time, you'll get 2 requests. You'd tap it for the request you're expecting, see it blinking faster to confirm your tap, and then blink slowly again to request the 2nd tap. That second request would be your cue for worrying. IOW, the blinking is an alert against your scenario.