No, CAESAR II (CAESAR II) does not automatically include the reduction you describe as found in para. 302.3.6(a).

Italic values in Table A-1 indicate that the basic allowable stress at temperature exceeds 2/3 yield strength at temperature. Para. 302.3.6(a) says these allowable stresses must be reduced according to para. 302.3.2(e). Para. 302.3.2(e) says use 75% of Table A-1 (or take data from Section II, Part D, Table Y-1).

So... As I read the Code, you should compare the sum of sustained plus occasional stresses to a value equal to 1.33(0.75Sh) if italic numbers are used. That's about equal to Sh.

We have a general setting in the CAESAR II configuration that you can use to reset the Sh multiplier for occasional stress evaluation. It's the Occasional Load Factor under the SIF's and Stresses Tab. If you set that value to 0.01, then CAESAR II will multiply Sh by 1.01 rather than the default of 1.33. (You cannot make it negative and zero indicates the default of 1.33) But this is a global switch and it will apply to all materials in the analysis. This approach will yield conservative results for the "non-italic stresses" if your analysis combines "italic stresses" and "non-italic stresses".