Great question: Short answer - up to the registered engineer or architect - not specifically addressed in any code that would usurp the judgement of the design professional....Period.

Very Long Answer:
Lets start with section 2121 of the 6th Edition FBC - Building. These are historic prescriptive requirements and there has ALWAYS been confusion as to where and how they apply. Thus, we inserted the following section into 2122 - Reinforced Unit Masonry - to try and drive home that 2121 just does not apply to masonry designed in accordance with the provisions of TMS 402/602:

2122.1Standards.
The provisions of TMS 402/ACI 530/ASCE 5 and TMS 602/ACI 530.1/ASCE 6 are hereby adopted as a minimum for the design and construction of reinforced unit masonry. In addition to TMS 402/ACI 530/ASCE 5 and TMS 602/ACI 530.1/ASCE 6, reinforced unit masonry structures shall comply with Sections 2122.2 through 2122.10.
2122.2General.
2122.2.1
Section 2121 shall not apply where design and construction are in accordance with the provisions of this section.

Thus you are completely correct that the provisions of 2121 are unique and independent and offer no guidance in properly designing your masonry structure - unless you want to use them in their entirety in designing your structure.

Ok, now to the residential code. Not much help there. As you indicated, Figure R606.11(1) shows some interesting stuff but nothing that gives you the guidance you, as a designer, are looking for.

The provisions calling for steel girding all openings is a seismic provision dealing primarily with shear. For shear in residential wind design you are generally going to distribute your shear to solid wall sections depending on their stiffness and utilizing only the un-reinforced value of masonry. If your un-reinforced shear value of the individual solid panels is not sufficient and you have to design a reinforced masonry shear wall you would absolutely be reinforcing around all sides of openings --- but --- that is almost never going to be the case with residential design - and is rarely the case with low-rise commercial design. Bottom line is you are generally not going to see masonry under an opening unless it is there of crack control (not structural reasons).

R301.2.1.1 references the ICC 600 in which section 405.3.2 "Openings in Masonry Walls" gives some common sense guidance to put a bar on either side of openings over 6' wide and to make sure that any bars interrupted by the opening get distributed to both sides. For openings in residential structures this is about as good as it gets.

For large openings you have to make sure that the wall segment on either side will take the load from 1/2 the opening width. Where you have a number of large openings in a row this can be challenging.

Hope this helped.

Obviously, you are always going to put a bar over the opening.

​The 12" truss HJR will NOT meet the requirements of TMS 402/602-16 for cavity wall construction. Your wall system will have a total width of 13.5". The actual hjr width is 10". The wire/ rod in the veneer will only have 1 1/4" coverage which is not enough. The code also requires a rod in each face of the CMU. there are several options for anchoring the veneer, If you need seismic protection then you may need the rod in the veneer. I suspect not, The hjr  with a third rod is seriously labor intensive. The bricklayers have to lay brick under the outside rod without raising it. If they do bend it up slightly they will probably not get it to lay flat on the veneer and must take undue care to get the brick above to lay to the line as well as keeping the veneer below from being displaced. The best cavity wall reinforcing and anchoring system is one that utilizes what we call a hook and eye system. It has 8" HJR for the CMU with a double eye welded to it and separate hooks that  will connect to it and lay into the veneer horizontal joint. This is the best system for production and allows for vertical and horizontal movement of the veneer. Ladder type horizontal joint reinforcing is recommended in reinforced concrete masonry.
Be safe.
Jerry Painter, FASTM
[email protected]