For the cassette & shifter with there 10% off components, they were about 8 pound cheeper than bike discount who sell retail components so not that clear.
And BD also sell a huge amount of OEM stuff, because they have their own bike brands to access it.
You’re also trying to compare it to another country’s distribution situation too – you have no idea if SRAM in Germany were hugely overstocked on XX1 components, and needed to shift a bulk lot at discount.
Your warranty isn’t with SRAM anyway, even if you had an issue, regardless of whether it had a serial number rubbed/ground off. It’s with CRC. Doesn’t matter where they source the product.
I’d hazard a guess (based on experience) it’s easier returning and dealing with CRC’s warranty department than BD’s too 🙂