I'm not sure how you could get to that conclusion from the link? >[...] but actually it only takes around 1 processor to encode 1080p60 with our default settin

I'm not sure how you could get to that conclusion from the link? >[...] but actually it only takes around 1 processor to encode 1080p60 with our default settings (which is still better quality than the PI 4 hardware encoder) Power consumption is worse, yes, but that is not a huge issue for the raspicam/raspivid ecosystem you are talking about. If anything the price is a huge issue, so just buy the pi4 if the hardware suffices or the 5 if you need something better.