I came across a question on Boson Netsim asking what happens to a packet sent to a subnet in the same classful network with no existing subnet and the correct answer said it sends the packet to the default route or discards it if the ip classless command is configured. The question never stated wether classless routing was in use, which is the determining factor of wether the ip classless command is valid.
May I ask that you submit a support ticket for this question, please? If something is amiss, we'll fix it. If not, we'll explain why we did it that way.
Your question is a little confusing. If "classless routing is configured", then "ip classless" is configured. If that is the case, the default route would be taken. If "no ip classless" is configured, the packet would be discarded unless the default route was learned from OSPF or IS-IS, in which case "no ip classless" is ignored and classless routing rules apply.