It's not really a mainframe because the RAS story (Reliability, Availability, Servicing) story is sorely lacking compared to what a true mainframe gives you. So a midrange machine like AS/400 is probably a better comparison.
An AS/400 has a similar RAS story to mainframes than to Oxide/Dell. Oxide is closer to Dell (Oxide RAS is effectively the same as any sled hyperconverged) than they want to admit.
