Except for the cockpits, no it's not. But if legs shows up, the problem won't be "where do we fit all this stuff", it will be "what the hell do we put in this giant blimp to justify it's outward size".
I'm just not SEEING* this. As Sylow points out, mass numbers make no sense to begin with, so trying to use those to imagine volume is a fool's folly (not calling you a fool, just using an idiom). I mean, look at massless AMFUs and fuel scoops - mass is meaningless in this game.
I served and lived on a submarine, and it's not just about "filling a volume". You need to be able to get those heavy torpedoes from the service hatch to the torpedo racks, which requires hallways and hatches and rails and equipment. You can't just arbitrarily say, "I'm going to swap out the sonar room so I can store more torpedoes". Nor will putting anything in the
middle of a submarine strengthen the hull (HRPs).
Also, we're not talking about a cubical Type-7 here. The Sidewinder, like grandma's attic, has some very tight, slanted spaces (which ironically might work great for reenforcing the hull but are rubbish for efficiently storing stacked containers).
Anyway, you are talking numbers, I am talking layout and visual design. That said, until I can watch that video, I'll take a break, but unless this video addresses all aspects of a functioning ship (including machinery, where SRVs are stored while scooping cargo, how scooped cargo is moved to the "wing tips", etc.), I'll not be convinced that modules are anything other than old-fashioned Dungeons and Dragons stats on a sheet of paper.
* I can't access that video from my current location, I'll have to look later.