Not a problem
A splitter is a directional coupler (with equal loss on each leg). AND they make directional couplers with different values of attenuation in the "down" leg also.
If you are using a splitter as a downstream combiner, there is little or no energy returned to the upstream. It might be 60 db. down which is negligible.
It has to do with the way directional couplers work and the way energy flows thru the toroidal core.
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