I don't like that idea either! Why 4 chambers for one engine?
As you may know, the heritage of the Soyuz family of launch vehicles goes way back to the R-7 ICBM, developed in the 1950s.
Back then, the Russians had problems with combustion instability in engines with large chambers. So, to avoid these problems they built engines with a single turbopump feeding four smaller chambers, instead of a big single one.