New more Secure Auto Routing

I am trying to upgrade some CI4 websites from 4.1 to 4.3 and was startled to see that _remap was removed and that instead of index we must define getIndex method. This requires extensive changes to my websites and makes for some very ugly method names in my controllers. I'm inclined to continue using the legacy routing. Can someone please refer me to discussion that shows 'current auto routing is a security risk' ? I'd like to see that discussion. I don't use any of the filter functionality, and this new auto routing doesn't really look like an improvement to me.