You misunderstood the article, Boeing is issuing new shares in order to bolster their cash on hand inventory. They’re issuing shares that didn’t exist before to raise new capital.
Boeing did $43B of stock buybacks in the 2010s. In practical terms those shares did exist before.
I don't know whether they retired the stock they bought back or put them back into the treasury, but in practice it's basically the same thing. Shares are fungible.
