AFAIK WhatsApps crypto isn't too old either but that doesn't seem to prevent HNs resident cryptospecialists from recommending it.
That said: I belive them when they say that WhatsApps crypto is stronger.
On the other hand I would expect them to leave a little note somewhere about WhatsApp being a data collection tool for Facebook that also still happens to works as an instant messaging platform.
It can take years, much like a car has to be crash tested, a new crypto algorithm must go through a certain process to be considered good enough.