Why are we still arguing about boarding time. It says what it says on the boarding pass and if things happen then things happen. The situation has been dealt with, the person still travels with CX and still gets to the plane on time. If he was promised a buggy then he was relying on what the lounge agent was telling him. Since the buggie never showed, he missed his flight; CX had every right to close the gate but the OP just relied on what the lounge agent was telling them.
I don’t understand why we have to berate people for their choices, if that’s what they want to do then so be it. I always show up to the gate just before it closes but I know what my risks are, if I miss my flight then I learn to deal with the consequences. Yes, the OP’s abusive verbal language is unacceptable but there’s always multiple sides to the story; he-said, she said is not a way to determine who’s right or wrong.