The function point does not return a center of lseg.
Before patch:
=# select point(lseg '((1, 1), (2, 2))'); point ------------- (-0.5,-0.5) (1 row)
=#
After patch:
=# select point(lseg '((1, 1), (2, 2))'); point ----------- (1.5,1.5) (1 row)