Pretty sure 10k AGL is pretty standard for most TACAIR aircraft in the US.
I would hazard a guess that in both ejections the aircraft were not an unusual altitude when they punched out. If an aircraft is out of control and at high speed starting the ejection sequence at less than 10k feet might not be enough to get out in time, especially in a multi-crewed aircraft. It takes a lot more altitude for your chute to deploy if you punch out upside down. And there are several instances, including at least one in a Prowler, where the folks who ejected earlier in the sequence got out but the folks who got out just a fraction of a second later didn't make it (in the Prowler there is a 0.4 second gap between the seats; ECMO 3 goes at 0.0, ECMO 2 at 0.4, ECMO 1 in the front right seat at 0.8 seconds and the pilot goes a full 1.2 seconds after the handle is pulled). The Prowler mishap I am thinking of happened in '96 or so and both backseaters made it out with injuries but the front seaters didn't get out in time.
So 10k might seem a bit high to some it really isn't.