So your point is, nothing? Other than a similarity of wording, the questions aren't similar at all. They are exact opposites.
But I've noticed that you argue nothing, at least in this thread, just to have something to argue about.
Because the rules ay it's limited to 10 minutes of air, and unlike water there's no pressure differential to say otherwise.
Air pressure varies at different altitudes and different temperatures. Why is it wrongbadfun to ignore water pressure (or assume magic takes care of it) but not to ignore air pressure?
You've done plenty of analysis as to how much air weights, how much volume is needed to sustain a human, etc. Which rule should override? "The bag contains 10 minutes of air" or "this is how much volume the bag can hold, this amount is displaced by the contents so this is left for air, and it can sustain the individual for this long"?
As Vegepygmy notes, the thread asked for discussion, however it seems any discussion which disagrees with your viewpoint is dismissed as ill conceived "paisley dragons". So why ask in the first place?
You want the physics of water pressure, but you accept the lack of physics for air pressure.
You assume the bag expands enough to take on more water and burst, but not to take on more air than that 10 minute supply. "Because the rules say so" is really just "because magic", since there is no other basis offered for the constant supply of air, regardless of whether the creature inside exerts itself or relaxes to change air usage, regardless of the size of the bag and regardless of its other contents.
You assume that the normal rules of physics will apply to the magical bag unless explicitly overridden by the rules, and this is a fine basis to proceed on. But magic, defying physics by definition, means assuming normal physics is not the only reasonable approach for interpretation. "How would the spellcaster want this to function?" is also a valid interpretation, incorporated by one prior poster. The prerequisite spell for item crafting could also be relevant, but this one seems to have effects very different from the Bag of Holding, in that the spell actually sends the chest in question to another plane. Are there really two containers, one here (the bag) and the other elsewhere (the storage space)? If so, we still have no info in the spell for how that interface works - the spell contemplates no such interface, so it provides no guidance to assess how that interface functions.
Your interpretation is valid and, as noted before, your position that the typical PC would know about this before opening the bag underwater, so maybe the player should be reminded, as also valid. But then, would a reminder that stuffing a lance into the Bag is a dicy proposition not also be knowledge a PC would have? Should the implications of dropping a dagger point first have been canvassed by a knowledge check (or by another PC being able to speak while the dagger was being drawn, the bag opened and the dagger positioned)? Those can also be viewed as "gotchas" or as perfectly legitimate consequences of PC/player error. I might very well respond to the comment that a Bag of Holding is destroyed if pierced, with "my PC knows little of matters arcane, so he will proceed to drop the dagger/shove the lances in unless someone else does something to stop him", depending on the character.