The was my first thought as well. Yes, using the Safe Browsing list feels wrong, but I don't know enough to speak definitively in that regards. However wouldn't a relatively simple solution be that if a registrar is choosing to use some third party's list of banned DNS entries that the registrar then also implement sufficient unblocked components that will allow people to be unbanned from that third party?
> Add a DNS TXT or a CNAME record.
I haven't had a use-case for a TXT record come up yet, but isn't it low risk enough to allow domain owners to continue to configure TXT records even if the registrar wants to ban configuring other record types? Then the person in the article could prove ownership and could then get off of the third party ban list that the registrar was utilizing.