The GP might be referring to how most of the non-hyperscalers like Linode or DigitalOcean or Vultr tie total monthly egress to instance size. IIRC they do allow overage charges at $x per GB but it quickly becomes more expensive to do it that way.
You're right and by extension you have to put together a search in order to see exactly what someone has tweeted to someone else, by which I mean you have to pro-actively search in order to truly follow someone.
For instance, during the recent downtime I wanted to see what Squarespace was saying and what others were tweeting to them. There's now way to do that without doing a search for their username.
Tweets and replies only show replies to what an account tweets, which is virtually redundant when sat alongside the full 'tweets' stream. There was no quick click way to see what others were tweeting to them.
This compartmentalisation is a constant attribute of Twitter that they seem to actively maintain and even design towards. They expect you as a user to know what you want to see.
They need to be much more active about presenting data views to the user and take away the need for the user to try and extract meaning and relevance from the constant stream of data.