Sounds quite fishy :( . Any specific proofs in addition to all what have been said so far? I've checked the links, they don't really prove anything...
here are links to additional discussions from the time of the change: https://community.signalusers.org/t/mandatory-pin-is-signal-...
One of the few articles that talked about it at the time: https://www.vice.com/en/article/pkyzek/signal-new-pin-featur...
One of the many reddit posts by confused users who misunderstood the very unclear communications by Signal: https://old.reddit.com/r/signal/comments/htmzrr/psa_disablin...
here are links to additional discussions from the time of the change: https://community.signalusers.org/t/mandatory-pin-is-signal-...
One of the few articles that talked about it at the time: https://www.vice.com/en/article/pkyzek/signal-new-pin-featur...
One of the many reddit posts by confused users who misunderstood the very unclear communications by Signal: https://old.reddit.com/r/signal/comments/htmzrr/psa_disablin...