[disclaimer: I work at Brex, but am not speaking on behalf of the company]

I think one thing being lost in translation here is that Brex considers small businesses to be different from startups, and it's an important distinction internally that is likely getting lost externally.

For example, we just acquired Pry to help with founders at small startups figure out financial projections and needs. If you're an early stage funded startup, Brex is probably still a good fit.

The policy cited here is more about no longer being a good fit for "traditional" small businesses.