Heat Treatment requirement per AD2000-Merkblatter

The DIN-ASTM Equivalent table

Design Data:

Design Temperature : 380degC , Design Pressure : 31 barg
Operating temp : 850degC , Operating Pressure : 25.5 barg
OD = 610 MM, SHELL AND HEAD THICKNESS : 18thk
MATERIAL A 516 GR 70

As I refer to ASTM Equivalent material for DIN ( see attachment ) , The plate A 516 GR 70 = P355GH ( DIN 17155 19Mn6).
We haven't buy the plate since the argument on the material equivalent issue.

I got consultant calc stated that the plate A 516 GR 70 IS EQUIVALENT TO P265GH AND NOT P355GH.
ASTM Equivalent material specification states that P265GH IS = A 516 GR 60. Comparing THE YIELD STRENGTH for both IS 260 N/mm3
which is is similar as A 516 GR 70 if we buy plate as per ASTM.

For EN10028.2 this plate of P265GH is normalised AS THE END PRODUCT.

I need technical expertise on this if I misinterpreted the AD2000-Merkblatter HP 7/2 : heat Treatment of Ferritic Steel, especially on the heat treatment on the head.
As in this section , Item 2.5 stated that the cold formed head need heat treatment after forming. The problem is category of A516Gr70 equivalent per DIN standard. My head thickness is 18MM .