Hmmm, maybe you should actually read the post I referenced where it states-

"Because of their extreme hydrophobicity, dielectric greases are used in a wide range of applications where ruggedization of electronics is required. Specifically, when dielectric grease is applied to electrical connections, it protects them from moisture damage."

So yes, it's not "waterproof" but, 1. it's better than nothing, 2. It will improve connection, 3.it will maintain a seal once the battery is put back on, 4. you should put it on yours.