Measurements of WETT wall clearance? Measured from stove backwall or from stove accessories/panels mounted on its back?

[Gmarcil]

I will be installing a Pionner Princess cookstove which has a hot water reservoir mounted on the back.

I would like to know if WETT specifications provide guidelines as to what constitue a valid end point to measure the back wall heat clearance?
Is it from :
- the combustible wall to the stove back wall (where firebox is located)?
or
- the combustible wall to the stove back hardware and accessories?

The UL certification plate on this stove (shown in the picture below) stipulates the following:
- A Unit to backwall = 25 inches
- Backwall to chimney connector = 20 inches

As noted, there are no specifications about the case of an optional mounted water reservoir. This unfortunately leaves room to interpretations!

Therefore should the clearance measurements be from:

- the combustible wall to the back stove cooktop plate extension? (see attached pictures)
or
- the combustible wall to the hot water reservoir outer wall?


This cookstove has a reservoir mounted on the back which is heated by a cooktop plate extension of about 3 inches as shown in the attached pictures.
You can also see a detailed video here: Hot water back reservoir

Two different WETT installers/inspectors came by for a consultation. Their recommendations about the installation was different due to their interpretation of wall - to - stove distance !?

So my question is: What is measurement end point at the stove?