I think that he meant that he put grease on the posts AFTER the terminals were in place and tight. This is a good thing to do to keep corrosion under control. The WRONG way to use grease is BETWEEN the terminal and post.

When I was in the Army it was required that grease be spread over the battery terminal after it was tight and in place. (I'll bet everyone thought that the Army only had horses and mules back in the days I was a GI.)

I think that under the back seat is an EXCELLENT battery location. It frees up room under the hood and goes a long ways toward better weight distribution.

Have a great day,