applicability of GST on employment bond in PSU

As per clause I of schedule III, ‘services by an employee to employer in the course of or in relation to his employment’ are out of the purview of GST. It is important to note that services in the course or in relation to employment are out of the purview of GST. The provision does not include services to the extent of consideration by way of salary. It implies that any other considerations paid to employee usually in the course of business may fall under this clause.

but when we sign a bond we sign it before becoming employee of company as party to the bond contract.
then why it shall be covered under employer-employee relationship?