It might be okay to use the softener bypass occasionally but it should be noted that the bypass is a frequent trouble spot when they are used often. They are designed to let the maintenance folks bypass the softener on the occasions when they need to service the softener and are not really well built for frequent use.
Far better option is to plumb in a faucet before the softener as the water is then certain to be untreated where just letting the water run may or may not clear all the salt content, depending on the way the house is plumbed.
Considering how many folks do routinely add salt to their tanks as a disease prevention, I'm not sure the salt content is enough to worry about.
But it is an unknown wild card which I like to avoid. Just another issue to confuse us, perhaps?