Using pygeos with GEOS 3.7.1, line_interpolate_point behaves differently, see implementation in src/ufuncs.c.

import pygeos
multiline = pygeos.Geometry('MULTILINESTRING ((0 0, 2 0), (3 0, 3 6))')
pygeos.line_interpolate_point(multiline, 0)

this returns POINT EMPTY with GEOS 3.7.1. The expected result is POINT(0 0), as correctly returned with GEOS >= 3.8.0.