So further to my comments above.  I just looked at my Panasonic telly.  And plugged a usb stick and it said I could use it for recording. 

before formatting it there was a big warning saying it’s only accessible on tv. This tv.  And if the tv goes in for repair it may not be accessible when it comes back.  I assume that means it encodes with serial number or something like that.  It explicitly mentioned it’s not readable on a pc.