The specs on combiners are always tough to figure out. What most people think
of as 'insertion loss' is actually division loss. The1 to 2 splitter with 3.5
dB insertion loss probably claims 3 dB of division loss --and 0.5 dB
dissipative loss.

Its very unlikely its 3.5 dB of dissipative insertion loss. Even cheap power
dividers--which are split delay networks with chip resistors--tend to be better
than 3 .5 dB of dissipative loss, when they work.

73,
Chip N1IR