Really, not a lot about Tezumak makes sense. Clearly the ancient League is intended to be analogs of a lot of the contemporary League they wind up fighting. But Tezumak is more like Steel, who doesn't seem to be involved in this incarnation of the League.
Why is a power armor guy there? Other than the fact that this story was written with a viewpoint that the best superhero fights are the whole team fighting a single something that's HYOOJ AND STRONG, wouldn't it have made more sense and lined up better to have him be some ancient warrior who thought that the metal seared into his skin and bathing in the blood of his fallen foes is what let him access the Speed Force?