Testing an A/C vacuum switch

[ThreeQuarter]

What is the right method to test an A/C vacuum switch? What does success and/or failure look like, exactly? I'm using a hand vac pump (made for bleeding brakes) on port 1 and plugging port 2 and 3 simultaneously, then checking to see if it can hold a static vacuum up to 15inHg. I'm clocking the switch in the positions it is in when installed in the A/C control head. I understand my method tests for vacuum sealing and not for whether it properly routes/releases vacuum to the right port (which it does do).

Back story: I bought a reconditioned 3-port unit that does not hold a vacuum at all per this test. This is the same result as the OEM 3-port unit I was hoping to replace. And those results are in contrast to an OEM 2-port unit I have that does successfully hold a vacuum. The seller of the reconditioned unit says I am testing it the wrong way and that the reconditioned unit tested fine when it shipped. I made a video and posted to YouTube (keep in mind the 2-port unit does not have a cap on port 2): https://youtu.be/DZZ7Emtmm-Y

What am I missing--how could it be acceptable to leak this much vacuum, regardless of whether it's downstream of a vacuum reservoir? Not interested in heeping scorn on the seller, just hoping to understand this part better so I can make sure I'm asking for the right things. I always learn a lot from the collective experience of this board.