In his book, Mr. Peng presents a lot of sound engineering details not covered by a standard as B31.3.
It is hard to say that applying them when Contract is asking only for B31.3 means you are "right" and the rest of people may be "wrong". Eventually you take your responsibility, they take their responsibility.

Or, reading the following in B31.1 NONMANDATORY APPENDIX II, what it is your feeling about "wrong" or "right" approach?

"Two types of seismic bending moments occur. One type is due to inertia effects and the other type is due to seismic motions of pipe anchors and other attachments.
As will be shown later, the moments due to inertia effects must be considered in eq. (16), para. 104.8, in the kSh category.
Moments due to seismic motions of the attachments may be combined with thermal expansion stress and considered in eq. (17), para. 104.8 in the SA category. For this reason, it may sometimes be justified for the designer to consider the moments separately; otherwise both sets of moments would have to be included in the kSh category."

Maybe you would understand that sometimes you are allowed to be "right" otherwise you have to be "wrong"?

For sure looking in different codes you can see different approaches. For example API 650 mentions in Table E-8—Design Displacements for Piping Attachments values under the column "ASD Design Displacement", so at least it is clear they expect you'll input the values in an ASD method. They mention in text "Unless otherwise calculated, piping systems shall provide for the minimum displacements in Table E-8 at working stress levels (with the 33% increase for seismic loads) in the piping, supports and tank connection"

I'm afraid the discussion may continue with no "right" conclusion.

Returning now to B31E formula, I would think that without additional clarifications, that formula must be considered in a conservative way and that means to consider seismic loads as they are defined by ASCE 7 (including the displacements calculated for ASCE loads). Knowing no details about the formula am I wrong or right?