maybe that has ended

I suspect (but don't have evidence for this) that sponsorship tends to snowball -- corporations become more likely to sponsor products that are already being sponsored; and the harm from users thinking that the project has "enough" funding might be outweighed from the benefits of users and orgs thinking, "it's normal to sponsor Krita, we're not doing something weird or experimental by jumping on the bandwagon."

Again, just an instinct though, I could be wrong, and I get that this page being part of a larger existing funding platform might make including direct sponsors more contentious or inappropriate.

As a software engineer I understand what you are saying, but it is incredibly misleading then.