The idea of your system sounding great with a full loom or a complete mishmash says absolutely nothing to answer the question. Unless you have compared the opposite… there is no information gleaned.
In my fifty years of pursuing the high end, owning dozens of components, and hundreds of interconnects… with slow and methodical convergence on synergy of components and same interconnects and cables is however evidence… although somewhat indirect.
I do have a theory for which I have a lot of personal evidence. But would be hard to prove (like everything in high end audio):
If you consider a sequence of four components Streamer -> Amp or TT -> amp)… each with a different small shortcoming.
To make it simple, let’s say component one rolls off the highs, component two rolls off the low frequency, component three rolls of the highs and component four rolls off the lows. By the time you hear the output has a highly attenuated high and low frequency. This is a pretty strong case for all the same components.
Then apply the same logic with all cables and interconnects. Suddenly the same components and same carefully chosen interconnects become a much more synergistic collection of gear.
The real world is much more complicated… but this really suggests the same everything will provide the best sound.
Of course if a different company produces a much better single component you have to weigh the variables. But if a company produces outstanding components across the spectrum, then they have a real competitive edge.