Some codes allow a beam to follow slab flexural shear minimum reinforcement rules if the depth is less than half the width. But beam width alone is not a consideration. It would also depend on the support conditions and depth!
These rules are intended for wide, shallow beams, commonly known as band beams. The rules have changed several times over the years due to further research, and probably vary depending on the code you are using.
And by the way, this question is not really about formwork, but rather concrete design. There are several forums which would be more appropriate...for your future use of the site.
Not sure what you mean by the last comment about colleagues in designing slab/beam support. Do you mean for punching shear design? Something else.
This site is getting very difficult to answer questions on. We are all engineers who have technical training ands should know how to frame questions that we want answered. How about people give all of the information needed to answer questions. It makes it very difficult to answer anything when the details given are so basic and lacking in detail. (end RANT).
