I would imagine pretty low cost attacks such as a bed sheet or a piece of duct tape would result in a false negative, you are better off spending your money with a simple PIR motion sensor:

https://www.amazon.com/ISC-BPR2-W12-Detector-Coverage-Temperature-Compensation/dp/B0191U3IZS

Or:

https://www.amazon.com/Bosch-BDL2-WP12G-TriTech-Motion-Detector/dp/B0056Z3W6I

Use the CV models as an awareness tool instead of your primary detection mechanism.

Sorry as its probably not what you want to hear.

Frigate has made some big strides in the CV space for home security and some people have gotten great results. Currently it is just very resource intensive to do live video recognition without some sort of more basic motion filtering first.