As the others pointed out - it is NOT the drain bolt, but it WILL drain all that leg's fork fluid out if it isn't sealing against the bottom.
When refurbishing/rebuilding forks, that little aluminum crush washer up under that allen-bolt should be replaced as a matter of course - they cost about a dime or so. Sometimes once gets lucky and can successfully re-use them, but the last time I did this, it didn't seal, cause all the fork oil in that leg to drain out while riding 40 miles over bumpy tarmac, and coated the brake rotor with fork oil. The loss of braking power was the first indicator that something was going seriously wrong. So, I had saved a dime, but ended up buying new brake pads and having a slower ride back home to re-do the fork filling, etc.- fortunately the LS has dual front brakes! I won't try to save that dime again.