I know that to some extent I’m yelling at the cloud. I’ve mostly seen this feature on new Toyotas, but I also recently saw it on a new BMW.
The CHMSL flashing feature seems to happen when a person first applies the brakes after a period of not using them. It blinks the lamp three times before leaving them on constantly. This feature might be useful when traveling at highway speeds and it’s been a long time since the person has put their foot on the brake, but when traveling in city traffic it seems that the light is just strobing constantly. With modern LEDs there is no warm up time, so it’s like a red strobe light is going off at eye level.
The last update I found on Wikipedia said that the lights were generally not permitted to flash, with a couple of linked rulings from 2010.
My searching for details found various forum questions and answers, including how to add blinkers as after market options, but no details as to where the rules may have changed, or if it’ll be a new requirement going forward.
I certainly hope that it’s a temporary trend that goes away.