It's not a euphemism for corruption.
Quite literally a bank is not required to make you a business account. A bank is not required to give your business a loan. The list goes on.
SVB was much more willing to do things other banks wouldn't for startups; this is what people mean.
Now, there are a bunch of claims that SVB gave startup founders discounts on personal mortgages for having their business accounts there. This is just gravy on top of the fact that SVB may have been the only bank to accept the business account anyways.
