Yeah, by all means, the device should probably not send double events. If you haven't clicked "Configure" on the device page, especially if you changed the driver yourself), that may help, especially for a Zigbee device where it configures how/what the device reports to the hub. I should remember to check my lock when I get home (I'm assuming you mean the BE468GBAK, the only Zigbee Schlage Connect). If it's happening with a lot of different devices, I wonder if you're having some sort of hub problem. I wouldn't reach that conclusion quite yet, but a soft restore is generally pretty painless and might be a good first step if you do. It sounds like your lock might just be sending two events, a "plain" unlocked event and another at the same but with a type of "manual" specified (this is the "physical" vs. "digital" difference, so thumbturn vs. keypad in the case of a lock) and the driver might just want to suppress the "plain" one, assuming it consistently reports both.
Back to the notifications: I'm not sure how the Notifications app implements this suppression behind the scenes. It's possible you may be able to make Rule Machine do a better job yourself in a manner similar to those for contact sensor suggested above. This is a second-best option, in my opinion (best would be the driver level, but we can't control that directly).
