Already demonstrated how faulty it is using controllers to assert that a console is a "spiritual successor" to another console.
I.E. Playstation 5 uses ergonomics clearly inspired by the Xbox One, doesn't mean the Playstation 5 is the spiritual successor to the Xbox One.
Or the Switch Pro controller is also inspired by the Xbox controller, doesn't mean the Switch is a spiritual successor to the Xbox.
Every company takes design cues from another... A good idea is simply a good idea... Again, Sega wasn't the first company to have ports on the controller for expandability, the Nintendo 64 did it a whole generation earlier.
As for the ABXY arrangement, there is only so many ways you can take that approach... And is an argument that is questionable at best.
Six-face buttons has existed for a long time... Again. The Nintendo 64 did it with it's 4-C button layout plus A+B buttons, doesn't mean the Dreamcast was the spiritual successor to the Nintendo 64.
The Xbox used the secondary white/black buttons mostly as start/select for the most part.
See, here is the difference you aren't taking into account. The Playstation and Xbox are concurrent products, same with Switch and Xbox. You can't have "a spiritual successor" when the other company is still in the market. At that point it's just a competitor. But the Xbox and Dreamcast were not concurrent products. This is why one can be considered a spiritual successor. The "spiritual" part meaning not direct but heavily influenced by.
"Every company takes design cues from another"
And the vast majority of Xbox's design decisions were taken from Sega which NO other manufacturer was copying at the time. Nintendo abandoned its controller ports, Playstation never even copied it...why did Xbox?
"Six-face buttons has existed for a long time....Again. The Nintendo 64 did it with it's 4-C button layout....doesn't mean the Dreamcast was a spiritual successor"
Okay, Dreamcast didn't have six face buttons, the Sega Saturn did. And again, concurrence.
"The Xbox used the secondary white/black buttons mostly as start/select for the most part"
This shows me that you didn't even play an Xbox. The Xbox controller had Start and Back buttons. It had no need to use the white and black buttons as start and select. Literally every game I played the "start" button did exactly what it did on other consoles.
Also, you're trying to explain away individual instances, but it's all too coincidental. The Dreamcast and Saturn featured many things that the Xbox would eventual feature. They had similar controllers, both aesthetically and functionally. Microsoft worked close with Sega for the Dreamcast, which inspired them to enter the console market and compete with Sony. They entered exclusivity contracts with Sega during the early years to remain competitive with Sony. Bill Gates even conversed with Sega about Dreamcast backwards compatibility. It isn't JUST about the controller design. It's about the influence on the console overall, which was shown by third party relations, focus for the console, and controller features.