Bread has few ingredients, but there are many other factors that can create completely different results.
@furopoi technically yes- the amount of gas is proportional, but the reduced amount of yeast greatly reduces the amount produced and slows rate of fermentation. Even though it wasn't mentioned, a guess here is that the MC used some form of retarding/refrigeration for the bulk fermentation to slow it further. At the same time, the starches have more time to get hydrated- this gives the enzymes present in the flour a longer time to breakdown starches into accessible sugars. This allows for more sweetness of the dough to be accessed during proofing and for more to be present when tasting the finished product. thefreshloaf.com has plenty of info on these techniques and some people post about the science in particular. Food scientist and writer Harold McGee explains this process in detail in his book Keys to Good Cooking.
In regards to baguettes -
this recipe is phenomenal- http://www.thefreshloaf.com/node/17415/baguettes-l039ancienne-cold-retardation
It is creating what is commonly known now as "pain a l'ancienne" (even tho the technique is modern and was created in the 90's throughout multiple french bakeries trying out long term bulk refrigerated fermentation). It is WELL over 15 hours tho, but used cold fermentation, and like the MC, less yeast than recipes it was adapted from. The MC in this manga obv has access to commercial equipment, etc, so that may create differences in technique overall. Earlier chapters talked about water, and the Japanese palate enjoying softer breads, so that may complicate what the spring princess loaf actually tastes like, but the above recipe seems closest in both concept and result- it uses a hard wheat, and slow fermentation both in lowered yeast and refrigerated dough, along with multiple turns (punch downs as the MC mentions) during the early fermentation stages.
Perhaps the closest style to the bread in this chapter would be the baguette at Duc de la Chapelle, Anis Bouabsa's bakery in Paris, which won best baguette in Paris some years ago- talked about here- http://www.thefreshloaf.com/node/8066/great-baguette-quest-n%C2%B03-anis-bouabsa
Like Masaki- VERY little yeast, 3 separate turns (punch downs) in an hour, and fermented over 20 hours. Neither of the above recipes have added malt that Masaki talks about- many bakers add it to increase accessible sugars and promote browning for the crusts, but these 2 recipes rely on the enzymes to work over hours to break down the starches to do the added work.
@LordTrollbias Food science is indeed a frighteningly vast field =D
@rpapo ah nvm about my translation question confusion- I reread the last chapter and see the translation of coupe here as cuts, and seems coupe is continuing to be used to describe scoring/grigne/ears from there on.