Microblogging with ActivityPub

I'm thoroughly stumped every time I read about Mastadon not having some feature X across instances.

I use the stock Mastadon app, and I have two views:

(1) search
(2) home

Both work fine across Mastadon instances. My home screen shows me a timeline of multiple people I follow across multiple instances. And their boosts of people on yet different instances.

Search defaults to showing me what's happening "in my corner of Mastadon", which by and large shows toots/posts from other instances. Search works fine across all multiple instances. I found Takei by typing "Takei" .. and he is on a different instance.

Yet numerous other reports talk about how you can't search across instances, and this article states I should not have "access to the federated timeline where posts from other servers may be viewed. " in the vanilla Mastadon app. Yet I'm staring at something that really seems to match that description. Unless you want it to include all toots across all servers.. including from folks you don't follow? Which seems.. overwhelming.

What am I missing?