"Fairly sure", well why didn't they say that in their blurb!?
The site copywriters seem to have very carefully made associations with Harvard whilst maintaining perma.cc as a separate entity to which they, Harvard, owe no obligations.
"Perma.cc was built by Harvard’s Library Innovation Lab and is backed by the power of libraries."
They built it, they organise it, but what they don't seem to do is provide any guarantees with/through/towards it.
Sure, who wants to take on obligations, make promises. Much easier to hide behind vague expressions of how great librarians are (it's a noble calling). 'Trust me bro' is pretty hard to go with for commercial enterprises regardless of who started them.
They clearly thought through the future, hence the 'we don't owe you anything when we sell the service to X/Alphabet/Meta or whoever' language.
How much budget have Harvard set aside for long-term maintenance?
Being literal librarians, I am fairly sure the creators of this service have thought through how it will remain accessible in the long term.