Building Code?

I was contacted by a company that is a modular builder of residential and commercial buildings here in Mich. that a "new" building code says -
(2015 MRC). Section 1003.9.1 requires that all chase covers have a 4" vertical lap (skirt) and a minimum 10° slope on the horizontal surface.
The 10 degree slope on the horizontal surface is the issue.
My question is, would this be for "new construction" or even if the homeowner was replacing his own chase cover"
I researched this and this is what I found on a different code
R1005.4 Factory-built chimneys. Chimneys for use with factory-built fireplaces shall comply with the requirements of UL 127. The metal chase cover shall be sloped a minimum of 10° to shed water. Metal chase cover shall lap down the chimney wall a minimum of 4′′ (102 mm) and be sealed with a suitable sealant.

The reason that this came up, is that they want me to supply and install some chase covers for them, and they said that they needed them per this "new" code. My inquire was to see if this code was for new construction only, or if it applied to anyone replacing a chase cover. I didn't know if anyone out there understood building codes.

I checked with an inspected, and this is what he said...
"The deciding factor as to the design of the chimney cap is whether a customer needs a mechanical permit to perform the work. If it’s a DIY job a basic old style cap will be ordered by the homeowner and no permit will be pulled.

If, on the other hand, a licensed mechanical contractor is hired to perform an installation; be it a modification or new install, then the design is based on a few things.

If the chimney already exists, then it’s dependent on how much of a modification is being made; entire new system, chimney only, or repair? A new installation would certainly need a permit and when the homeowner goes to their local code commission, they typically need to let the code official know the extent of the job and can then be informed of code requirements.

The design of the cap is determined by the date the permit was pulled and what version of the code is/was in effect at the time. That said, it also depends on whether or not the mechanical contractor knows the code, and if the local inspector also knows and/or enforces the code. J

In our case, since we only install “factory fireplaces” (Heatilator, etc). We need to meet the requirements of the code that is in effect when we start production on the home."