These is correct, although it only has to be +70 rpm for a certain amount of time, it automatically senses the angle then. I found this out the hard way the day before an event when I changed the battery and no power was displayed (it was because I was pedalling clipless pedals in my trainers, just doing a system check, and never getting above 70 rpm, an hours panic and going to a bar to get a wi-fi connection to research the issue was stressful.) As soon as I put my cycling shoes on and got to 70rpm for half a dozen revolutions all was good. This was for Vector 2S, not sure on the RPM needed for other versions.
PS I had a Wahoo head unit, but no head unit is needed. There is the Garmin app where you can set the crank length 172.5mm is the default if not set. You can set the crank length in various head units as well, if not set correctly you get slightly higher or low readings depending on the length or your cranks vs the value set, 172.5mm if you’ve not set it.