Leaderboard

In reality, load/moment transfer depends on relative stiffness of columns and beams. When you model a whole building, the software takes care of relative stiffness automatically. For manual calculations, there are various methods. For example in above image, replace the pin supports with actual columns and try solving this Moment Distribution Method by hand and compare the results. Or make a computer example of above frame in elevation with actual columns and try reducing/increasing column sizes to see what are the effects.

For braced frames, the beams are intentionally kept pinned as you don't need to have a moment connection for load transfer as brace takes care of it.

You might be doing it because the scope of problem is only to design beams. It might have some affect. You can check.