iOS 12.1 allows bypass the passcode to see all contacts private information. Feature? Flaw?

In Summary :

In a passcode-locked iPhone with latest iOS 12.1 You receive a phone call, or you ask Siri make a phone call (can be digit by digit), and, by changing the [...]

kindly refer the following link as follow up :
https://www.youtube.com/watch?v=ojigFgwrtKs