Towing Chevy HHR - Question

I just bought a 2007 HHR & had Base Plate installed.
I see that the suggestion is to pull FUSE #8 / Ign. fuse .... to avoid battery running down.
I unplugged mine in driveway just to see effects ... and there were a few ... but some items still worked ..... i.e. - warning light bulbs ^ more.

I was expecting EVERYTHING to go out ..... but that did not happen.

Does anyone with an HHR know if that is NORMAL , or NOT ?

Richard
'02 Damon Challenger
S. Carolina