I know almost nothing about non-profit fundraising, but this benefits tier membership model looks very familiar as a tech for-profit service, rather than a charitable non-profit for the benefit of all.
(Specifically, in a tech, like a SaaS, the free tier are sales leads and inflated "market share" numbers, and the premium tier are the real customers of the service value you're providing and is your whole reason for existing. In a charity, however, you don't measure out benefits based on how much that person is paying you. Though a charity will have special recognition for exceptional donations, like the donor's name listed on some page, or mentioned as a sponsor of an event.)
Given the dire runway situation they were in, I wonder whether they sent out a recent urgent appeal to their free-tier, as more like a charity, asking for donations? (And if so, was the obvious benefits tier model hurting any charitable goodwill they might've otherwise generated?) Or did they try to push their free-tier members an upsell to their premium tier, like a business? Or neither?