The downside is to use correctly you are supposed to split a log in two equal pieces, let both pieces rest for 24 hours, then take a reading on an inner (newly split open) surface,
source (pdf file).
The guy in the video says weigh a sample log from your pile, repeat over time and once a log has lost 2/3 to 3/4 of it's weight it's seasoned. Interesting tip on that video is when bark falling away is a sign of lowerign moisture content.
I kinda like the ringing sound test in the short CSIA video, no meter, no weighing, just knock two logs together and listen.