If I exchange a propane cylinder, I am capable of judging if it is what it's supposed to be. No rust, clean valve, correct weight. I cannot judge whether I'm getting swapped in a battery that is going to die. A propane cylinder costs about the same as its contents. A $10k battery holds less than $1 worth of energy.
I cannot judge whether I'm getting swapped in a battery that is going to die.
Sure, you can. When's the last time the battery display on your laptop or cell phone lied to you? Battery monitoring tech has been reliable since the lead-acid days, and it's only gotten better over the past few years.
There'd be some redundancy in most cases anyway. A sports car might require two or three standard battery units, each of which would consist of numerous individually-monitored cells. An 18-wheeler might require thirty or forty of the same standard battery packages, or perhaps ten of a larger form factor (think 'AA' versus 'C' or 'D'). In both cases the vehicles would be able to limp on half-power or less, in the event of battery failures.
This objection is a complete non-starter, no pun intended.
Edit: By the way, those swappable battery modules are going to last a lot longer since they won't need to be fast-charged.
This is not a valid analogy.