One thing that Xenophon does frequently is to talk about a military group and then mention the leader in an absolute construction. This is somewhat characteristic of Xenophon, more than any other author I know if. Here are some examples (easy to search for ἡγουμένου).
ἐνίκησαν δὲ Λακεδαιμόνιοι ἡγουμένου Ἀγησανδρίδου
στρατεύουσι πάλιν εἰς τὴν Κόρινθον, Ἀγησιλάου καὶ τότε ἡγουμένου
ἧκον οἱ τῶν Ἀθηναίων ὁπλῖται, Δημαινέτου αὐτῶν ἡγουμένου
καὶ ναυμαχήσαντες πρὸς τὸν Πόλλιν Χαβρίου ἡγουμένου νικῶσι τῇ ναυμαχίᾳ
…etc… (I could have added more)
Also here’s a nominative absolute version for grins:
ἐκεῖνοι δὲ εἰσελθόντες σὺν τοῖς ὑπηρέταις, ἡγουμένου αὐτῶν Σατύρου…εἶπε μὲν ὁ Κριτίας…
Now following that common pattern, we can easily imagine, as Gemoll evidently does, that Xenophon’s mental idea was something like this:
τριήρεις περιπλοῦσι ἀπὸ Ἰωνίας εἰς Κιλικίαν Τάμω ἔχοντος τὰς Λακεδαιμονίων καὶ αὐτοῦ Κύρου
Xenophon, however, is using it in a ἤκουε statement, so his brain modifies it as he goes:
τριήρεις [now acc.] ἤκουε περιπλεούσας ἀπʼ Ἰωνίας εἰς Κιλικίαν …
Now he gets to the genitive absolute. How does his brain modify it, verbally, as he speaks the words aloud to his slave? Possibly by saying Τάμων ἔχοντα…
And finally, I don’t have an example of an accusative absolute where Xenophon treats the group of men and their commanders like this, but here is another nominative absolute example (a form being historically related, says Smyth, to the accusative absolute):
καὶ ἐν τάξει (οἱ Ἕλληνες) θέμενοι τὰ ὅπλα συνῆλθον οἱ στρατηγοὶ καὶ λοχαγοὶ τῶν Ἑλλήνων παρ᾽ Ἀριαῖον