It's still not a great tactic against a superior or near-peer force, as while the boarding action is happening, the rest of the fleet can choose to decimate the attacker. Actually, if it's realistic, it will be in the defending side's policy/orders to do so.
Even if the uncle kills the grandpa and Chris, they won't have a fleet left to take down all the people who would rebel.
Then again, the uncle basically has no good option. Even if he wins, he loses.
That ship and tactic are best for assaulting a smaller force with a bounty that's needed alive.
Edit: And now that I think about it, it's probably just the uncle not thinking (too focused on the prize in front of him) his strategy needs to change from the last time he did it, because he's probably not realized this particular strategy that works against small force will not work well against a large force, despite being the same kind of mission.