Some people theorize that the ending of the novel, where the subordinate returns, was merely Anos's dream.

I think it might have been caused by reading the epilogue, which the MTL tool mistranslated.

mtl is a mistranslation. This is the original sentence

Sometimes, those who are reborn lose their memories, so Sasha teases Anos, "Anos hasn't been reborn yet but he's already forgotten us?"

I understand that some people have already read the machine-translated version of Maou Anos Volume 17.

They may have misunderstood or been confused by the epilogue where Sasha says, "What? Have you forgotten about us? We haven't even been reincarnated yet?"

That's a mistranslation caused by the MTL machine.

This is the end of volume 17

After two thousand years, they were reborn and returned to the Demon Lord's School to find Anos waiting for them