I think slightly later in that video is actually a good example of the problems with believing their early design conversations before they knew anything about MMO writing - and why I'd actually be happier if they just owned up and said "yes, with hindsight that was never going to work, sorry"
And sure, let's think about where that all ends. We want to be able to sneak onto other player's ships while they're loading cargo (and then, according to elsewhere in the video, steal the ship)
So that means that cargo loading has to take a non-trivial amount of time, so that another player has time to notice you doing it, head over to your bay (you must now enter the hangar to load/unload cargo), stealth around, wait for the right moment, and sneak in. A painfully slow transfer rate for a T-9 pilot of 1t/second - over 10 minutes for a full turnaround, even if loading and unloading are simultaneous - would still make it near impossible to do this on anything much smaller than a cargo-fit Python. (Not that it would have to be the same rate for each ship, of course, but still, even three minutes sat on the pad for each cargo transfer would be painful! Especially at outposts...)
And it probably needs to be something you can't avoid happening to you by just logging into Odyssey or you end up with a situation where people wanting to sneak on board ships play the Elite Dangerous Espionage client and people who don't want their ships sneaked onboard play Odyssey, so no-one actually gets to board anyone else's ship.
And then once you've got on board, then what? Do you arc-cut your way onto the bridge, blast the CMDR with your rifle before they manage to switch to "walking" mode and get their shields up, and steal the ship. Brilliant way of buying and selling engineered modules from other players, I guess. Where does the other CMDR respawn? Does it count as a ship rebuy for them? What if the other CMDR suspects you're on board and logs off a couple of minutes after launch while you're still sneaking through the air vents?
These aren't unanswerable questions ... but the answers would involve a lot of rewriting of existing long-standing gameplay decisions (cargo loading is instant, insurance rebuys exist, your ship doesn't persist if you log out with another player around) ... and most current players are probably quite happy with those decisions being as they are, and wouldn't like them changed for an expansion they aren't even buying.