AIU the intent of this publication is not to further research but to make it clear to anyone that we need to move to post quantum cryptography ASAP.
If only AI safety research had a mechanism this clear. "We have proof that building the machine will kill everybody, so get to work making a provably safe version."
Could be one of the intents, but the main intent is reputation building.
That may be the intent, but it is very anti-science.
But the algorithm still isn't practical on existing quantum computers, or ones that are going to be around any time soon, so there's no reason not to publish in full.