You have a choice, both the vid and the guide as posted are pretty clear- either way works.
A) Turrets Out - expect corrosion/snapped bolts/ and replacement Turret rings as future proofing.
B) Leave Turrets in - spring compressors may be needed on the front unless you have another body to stand on end of axle you are fitting the spring to (as per Vid)
There is more swearing in option A), but may be necessary......
Not saying it can't be done but it might be a bit fiddly just for the sake of four nuts???
To get the spring out the shock needs to be removed as well. If you remove the turret then you can withdraw the shock from the top and then the spring is free to pop out when it has cleared the seats however if the shock is in situ then you need to compress the shock to get it out of the lower mounting hole and then the spring & shock can be removed together. Tricky to get through the coils to do this?
The turrets (and retaining rings) are one of those items that if you have never touched the suspension then they are well worth removing to check for condition and to make sure there is no corrosion and / or build up of dirt inside or behind them.