Definitions: issue of shares: letters of allotment: bonus issues
Just because a letter of allotment is renounceable does not mean it is provisional. For example, a public company making a bonus issue will, normally, issue renounceable letters of allotment to its existing shareholders. The shareholder is absolutely entitled to receive the free shares and the right is not provisional. If the shareholder renounces or sells their allotment then this will be treated as a disposal of the shares and not of the right to receive the shares.