"Perfect consistency is possible only to God himself, and a close study of scripture will show that he doesn't always make it." (1)
That was Poul Anderson's standard response to readers who spotted inconsistencies in his future history. A lot of inconsistencies in fiction can be ironed out if it is recognized that most fiction, even when the narration is in the third person, is narrated from the point of view of a fictitious character who may be mistaken. Merseians are mammals but with more traces of reptilian ancestry than Terrans. Or they are warm-blooded giving live birth but are not mammals, "...no kind of animal that Terra had ever brought forth." (2) That last remark is obviously correct. The statement that they are mammals is made from Flandry's point of view. The statement that they are not is made from another character's. Thus, the statements express different characters' understandings, not objective facts.
In A Circus Of Hells, Flandry greets Tachwyr the Dark of Merseia as a member of the Vach Rueth whereas The Game Of Empire presents Tachwyr as the Hand of the Vach Dathyr. We are to understand that Tachwyr has risen to the Handship of his Vach between novels but the Vach should not have changed. But, of course, Flandry could have been mistaken. This would be out of character but is at least possible and A Circus Of Hells does show him making youthful mistakes. Flustered at meeting his former acquaintance unexpectedly in the formal setting of a Naval reception, Flandry could have stumbled and misremembered Tachwyr's Vach, like introducing someone as Northern Irish when we should have known that he was Scottish. Alternatively, there is a Story To Be Told about why, against immemorial Merseian custom, Tachwyr did for some reason change his Vach. Again, changes to immemorial custom are at least possible. The only logical impossibility here is Tachwyr both being in Vach Rueth and not being in Vach Rueth at the same time.
In "Honorable Enemies," Flandry says that Chereionites have full citizenship in the Merseian Empire whereas everything else that we know about Merseians entails that they either subordinate or exterminate other races:
"... the highest end of all...absolute freedom for our race to make of the galaxy what they will." (3)
That would seem to be incompatible with granting members of other races equal citizenship. However, the Chereionites are a very special case and, again, Flandry's information could be incorrect.
By referring to scripture, Anderson unintentionally invited comparison between his History of Technic Civilization and the Bible so how does Anderson's series measure up to this comparison? The Bible, like the Technic History, is a history of a people. Its books cover successive generations who lived in different but historically connected periods. Some books present alternative versions of events. Individual stories in Anderson's The Earthbook Of Stormgate and, in a separate volume, his account of the founding of the Terran Empire are presented as possibly fictionalized narratives of events that did occur. Further, some of Anderson's characters seek theological significance in the course of events. Thus, I think that the comparison with the Bible is valid.