Very intresting question.
In my opinion, there is nothing wrong in this approach. You can deliver goods at any time even if invoice is created earlier.
However as a transporter you have to take of E-way bill.
If you are transporting goods for which E-way bill is already created, then you have to transport goods within validity period.
If value of goods you are transporting is below 50,000 and supplier has not created E-way bill and goods are kept at location of supplier then there is not issue of delivering goods after few days of invoicing.