In SAO syntax : "7.3.9.3 Sample adaptive offset syntax"

The sao_merge_left and sao_merge_up flag are decoded depending on the following conditions :

CtbAddrInSliceSeg = CtbAddrInRS − slice_segment_address
(...)
leftCtbInSliceSeg = CtbAddrInSliceSeg > 0
(...)
upCtbInSliceSeg = ( CtbAddrInRS − PicWidthInCtbsY ) >= slice_segment_address

The Syntax Element slice_segment_address refers to the current slice segment, which may be dependent OR independent.

On the contrary, in HM software, this is applied only to independant slice segments, and sao_merge_up/left flags are allowed on dependent slice boundaries.

In the previous quoted text, I suggest to replace the variable "slice_segment_address" by "SliceAddrRS"