No they don’t. so assume you are currently a Hyliion shareholder. In order for the business combination to happen 2 companies must combine into one and have one equity base.
For that to happen, SHLL must buyout all the shares of existing Hyliion shareholders. To do that, it can pay cash or pay shares. In this transaction, it decides to pay shares to existing Hyliion shareholders. so if I currently hold 1460 shares in Hyliion, I will be compensated by SHLL 1000 shares.
At the end of the merger, all shareholders will hold SHLL share and the ticker will change from SHLL to HYLL.