If you are participating in the public beta, are an invited seed, or have a for-fee developer account and are using the beta, you may not talk about it at all in any public forum - https://beta.apple.com/sp/betaprogram/legal which you can get to from the link in the beta FAQ - https://beta.apple.com/sp/betaprogram/faq
These forums themselves have no rules about beta products, since anyone using an Apple Beta product has agreed to a non-disclosure agreement as part of their voluntary enrollment in the beta program. So these forums need no such rules since you’re legally bound not to discuss it, period.
“6.Nonuse and Nondisclosure of Confidential Information. Except as expressly permitted in this Section 6, you agree that you will not disclose, publish, or otherwise disseminate any Confidential Information to anyone other than individuals who are enrolled in the same individual seed as you, or as otherwise expressly permitted or agreed to in writing by Apple. You further agree to take reasonable precautions to prevent any unauthorized use, disclosure, publication, or dissemination of Confidential Information, including preventing access to or display of the Apple Software to third parties. You agree to use the Confidential Information solely for the permitted uses as set forth in this Agreement. You agree not to use Confidential Information otherwise for your own or any third party’s benefit without the prior written approval of an authorized representative of Apple in each instance. You hereby acknowledge that unauthorized disclosure or use of Confidential Information could cause irreparable harm and significant injury to Apple that may be difficult to ascertain. Accordingly, you agree that Apple will have the right to seek immediate injunctive relief to enforce obligations under this Agreement in addition to any other rights and remedies it may have.”
