I imagine because there was no source to back up the claim. There's definitely been an exodus of staff from the company in recent days, but it's not clear what the terms were. For some tweets from former Sencha staff who have departed over the past few days see my comment on another thread:

https://news.ycombinator.com/item?id=15365797

Edit: It certainly looks as though the entire team was let go based on the LinkedIn post you linked to in your edit.