This breaks down to two separate questions. Should I clean silicone lubricant off my grinder before use? and Am I loosing meat around the auger because of improper lubrication?
I should not say it is 'required' to 'wash or rinse' before use, depending on how long it has been since you last used it and how and where it has been stored. It is likely that at least some dust or debris has settled into the silicone since it's last use making (at least) a quick rinse a good idea though. If it was recently used, cleaned and lubricated and stored in a good dust free environment the 'need' becomes less...(but what could it hurt to do it anyway.)
A certain amount of loss is to be expected with parts that are typically rather loose fitting to begin with. A fresh coat of silicon (or oil) on the parts before use (and after cleaning) might help, but if your losses are significant I would expect that merely lubricating the parts are unlikely to improve things. A grinder is essentially a gravity and manual pressure feed device. Once you have pushed all the meat into the feed tube (and probably pushed it down with a plunger of some sort) those last bits are unlikely to 'push themselves' through regardless of the lubricant.