Rerounding effect

[Bas]

..with pressure a check has to be performed if the ovalisation reduction due to horizontal soil support is larger than the rerounding effect.

The way I interpret that chapter:
C.4.2.5.2.3 describes what you said above: When horizontal soil support reduction is larger than the rerounding effect (frr < dy2/dy1) horizontal support is allowed (disregarding water level for now).
In C.4.2.5.2.2: When horizontal soil support reduction is smaller than the rerounding effect (frr > dy2/dy1) horizontal support is also allowed, but only without rerounding.
(In both cases assuming internal pressure)