Yes when someone is sitting still, that’s a limitation of most “motion” sensors for home automation purposes, which are typically passive infrared (PIR) sensors
The problem is there aren’t many options for occupancy sensors (a more accurate term than “presence” for this purpose) that use technology other than PIR.
Here’s an example of one, but it’s not available in the US yet.
One workaround for occupancy (without motion) is to use a pressure mat sensor under couch cushions or mattress.
