beam column junctions

huangyhg

beam column junctions
nearly every beam detail i've seen anchors the top reinforcement at the support "downwards" into a column or wall. this often occurs with the bottom bars too.
however, the contractors will cast the walls and columns to the soffit of the beam (and slabs). to avoid uneven construction joints the engineer allows them to bend the beam anchorages up instead of down. thus the beam detail is reversed but an anchorage is provided and of course the wall or column is also reinforced to resist the induced bending.
if this is such common place, then why are the details always shown as bending down. will any latent defect be induced?
nb