I think we are taking Odo far too eagerly on his word.
In the "Way of the Warrior" scene, Odo thanks Bashir for covering his six. Bashir may think he saved Odo's life (at least if he doesn't stop to actually think
), but that's probably not what was at stake there. Nevertheless, what possible reason would Odo have not
to thank Bashir for saving his ass? It's mere common courtesy.
In "Vortex", we could say that Odo was merely playing 'possum to see how Croden would act. This would be an eminently logical thing for him to do. After all, for the first three-fourths of the episode, Odo had been led on a leash of Croden's lies. Now Croden had revealed that there was nothing worth Odo's time where he had promised wonders. Instead, Croden had done it all for his family. Finally the truth? Or another lie to let the con artist get away? Odo would need to know.
By pretending to be hurt, Odo could do a quick check on Croden's compassion and verify at least parts of his new story, namely the parts relating to his true character. If Croden made a run for it, Odo could easily de-knock-out himself and intercept Croden before he reached the runabout, then proceed to incarcerate the villain. If Croden returned to help, Odo would proceed to aid Croden in escaping instead.
Makes retrospective sense, even though obviously this wasn't the writer intention.