I'm not sure the "truth" lies in between these two methodologies. It may instead connect them at a diagonal.

My understanding of correct use of braces requires they exist in pairs (in general). For the most part the loading condition that requires bracing, wind for example, will likely work from more than one direction from time to time. In effect this means braces in pairs actually function as one brace. When a lateral load is applied to the system, one half of the brace pair goes into compression while the other goes on vacation.

When this condition occurs, the brace indeed can assume a tremendous load, but unlike most timbers in the frame, the load is assumed in true compression allowing a small section member to do a great deal of work. The timber which accepts that load from the brace however normally ends up dealing with bending and shear forces. For this reason I have been taught to think of braces more as pry bars than posts.

My experience with barn frames has shown that braces do indeed resist static loading as well as dynamic. Purlins in major/ minor roof system are a good example. The braces are typically placed across from one another at the purlin posts which allows them to work directly against one another. Typically the brace legs are increased with the span of the purlin. Of course this pairing doesn't work at the gable end, but often the tie beams are hewn to "camber" making them much wider than they are tall at midspan. This works well to resist thr thrust of the brace.

From a load study point of view, I do consider it practical to reduce the span of a member by one brace leg if it braced at both ends. If however it is only braced on one end, as in your example, the span cannot be reduced. Conversly, if the brace is pegged you may want to increase the loading factors for the beam since from time to time the brace may end up in tension.

Not much here to relieve the dubiousness. Now if we can just get this straw to at least turn into silver