There is unfortunately no clear uniformly agreed description of what "washing (up)" entails. Most people probably associate it with acetone washes.
Anyway, boric acid should react with sodium bicarbonate by forming soluble sodium borate. If you just boil off the water, the water-soluble salts are obviously going to remain on your crack rock (so it would essentially be freebase cocaine mixed with sodium chloride, borax and excess sodium bicarbonate).
If you separate your chunk of crack from the water, most of the borate ions should remain in the watery phase; however, crack-making is still a relatively crude process when compared to a "proper" freebase extraction using ammonia and ether, so even the world's nicest hunk o' crack would still contain a significant amount of impurities. However, impurities in crack are generally much less of a risk factor than suffering chemical burns and/or chronic lung inflammation from breathing in ammonia, blowing up your "lab" with ether fumes or setting yourself on fire a la Richard Pryor (turns out that caustic and explosive volatile substances should not be handled without proper training and equipment, and especially not by people impatiently fiending for their next hit of base).
