You are right. For one row of 5 cables, you can use the tables, but not for two rows.
A remark about IEC 60364-5-52 standard at first.
Annex B it is only informative, and the ampacities shown here are in order to exemplify a new mode of presentation and these are not correct values.
The A annex is still for calculations. See, at first one of the following tables:
Table A.52-2 (52-C1) – Current-carrying capacities in amperes for methods of installation in table A.52-1 (52-B1) – PVC insulation/two loaded conductors/copper or aluminum Conductor temperature: 70 °C/Ambient temperature: 30 °C in air, 20 °C in ground –column D, or:
Table A.52-3 (52-C2) – Current-carrying capacities in amperes for methods of installation in table A.52-1 (52-B1) – XLPE or EPR insulation/two loaded conductors/copper or aluminum Conductor temperature: 90 °C/Ambient temperature: 30 °C in air, 20 °C in ground –column D.
And then see:
Table A.52-18 (52-E2) – Reduction factors for more than one circuit, cables laid directly in the ground –
for 5 cables [of 2 conductors] 0.125 m apart. kred=0.65
For two rows of 5 cables per each row you have to calculate the current carrying capacity according
to IEC 60287-2-1 [and 1-1].
Table A.52-3 (52-C2) is calculated per IEC 60287-2-1 and 1-1.
The column D it is for 2 cables in a duct in 2.5 K.m/W Earth thermal resistivity and 0.7 m depth in a duct.
Reference method D, item 70 of table 52-3, (multi-core cable in ducts in the ground):
Cable drawn into plastic, earthenware or metallic ducts laid in direct contact with soil having a thermal resistivity of 2.5 K.m/W and a depth of 0.7 m.
According to your sketch there are two single core cables touching but without any pipe [or duct].
[so Rsd=0 and 110 cm depth]. Let’s say the resistivity stays 2.5 K.m/W.
The calculation according to IEC 60287-2-1 is very simple taking into consideration the cable data-conductor diameter 15 mm, insulated core diameter 17.8 mm and the jacket diameter of 21.2 mm.
The ampacity -per each cable-is then 120.7A.
Following DIN-VDE [from ABB vol.11-E-13] table 13-44, for 3 single core cables in triangle, aluminum I=305 A. From table 13-54 for XLPE, 20oC, 2.5 K.m/W, load factor 1[100%] f1=0.81. From table 13-56 for 10 systems 7cm apart f2=0.44. Then for 10 groups of 3 cables we get 305*0.81*0.44=108.7 A