You can do the 8919 without the SS-8.  But the client should be advised of the warning:

"If you enter reason code G, you or the firm that paid
you may be contacted for additional information. Use
of this reason code isn’t a guarantee that the IRS will
agree with your worker status determination. If the
IRS doesn’t agree that you are an employee, you may be billed
for the additional tax, penalties, and interest resulting from the
change to your worker status."