I don't disagree with you but at this moment in time it just seems a bit prudent to add something like this at the top:

"Arash – our co-founder and great friend – is leaving Dropbox for new adventures."

Just one simple sentence like that at the top lets us know the rest of the post isn't a eulogy, or at least not the kind where someone passed away.

Any other point in time when there isn't a global pandemic you can leave that out, but right now times are weird and confusing.

I think the “thank you, first name” format is common when a well known company founder or elder statesman is leaving. Here is Guido’s from last year. https://blog.dropbox.com/topics/company/thank-you--guido

And Arash is well known at Dropbox (and also here.)

Maybe you're right, I can't say that resonates with me but I may well be in the minority. I do find it interesting though that the post you link to has this as it's first sentence:

"After six and a half years, Guido van Rossum, the creator of Python, is leaving Dropbox and heading into retirement."

No ambiguities regarding the reasons for the post then.

(Also, for what it's worth, I had no idea who Arash was prior to reading this post.)

yes. changing the title is prudent at this time. I thought other way too!