I personally still can’t get any of these alternative commands to work on either of our two echoes.
Start Always triggers a music command, and Amazon support told me that “start” is a Music command not a connected home command. “Stop” is also a reserved word, used with things like timers and alarms as well as music.
I’m not sure what the deal is with “activate” is, but echo just doesn’t process that for me. Due to my disability, my voice is slightly slurred, but echo hasn’t had any trouble understanding me for anything else up until now.
I will keep experimenting.