Twitter's hostility comes down to jealously defending their business model. They declared war on third party clients about a decade ago, and that hasn't really changed. You'll note the API available under the new, looser, rules does not include any equivalent of the home timeline endpoint, which would be pretty essential to the client use case. A third party client could do things like not show their embedded ads (promoted tweets), or display the timeline in a manner more useful to the user than to Twitter's engagement metrics, and Twitter don't like that.

They've been pretty ok towards e.g. making your CSR tool interface with twitter to answer support requests over Twitter.

This doesn't really strike me as a change in direction, though it does look easier for people in the second category to get started.