Well the bundle used to say "16 steam keys included" and listed them; it doesn't say that anymore and has no steam keys listed. Their docs also mention that they generally turn it off for charity bundles, meaning this was most likely an accident. https://itch.io/docs/creators/bundles#hosting-a-charity-bundle .
"Generally, for larger bundles priced lower, we will disable all access to External (Steam) keys to prevent participants from having to generate an unrealistic number of keys. "
Admittedly the part about claims staying for people who bought it is conjecture from reddit discussions & some people here complaining about not being able to generate steam keys from their purchase https://itch.io/t/5910207/cant-find-my-steam-keys-anywhere#post-15462771 and from vague memory of a previous instance where that happened.