Hi Alex,
sorry about the confusion: as you noticed, the post in the Forum regarding the change in the PMP exam dates back to many months ago, when PMP candidates were expected to take the new exam starting July 1st 2020.
However, because of COVID-19, PMI decided to move it forward, mostly because of the restrictions around the world which could make it harder for many candidates to take the exam at a testing center, and not everybody can take it from home using the online proctored mode.
So, essentially, the news you found on the PMI website is the latest one and that is the one you should refer to in order to prepare for the PMP exam at your very best.
Good luck,
Gabriella