This reminds me of Soundcloud a few years ago when they were giving away API access for free for unlimited plays but then were almost close to bankrupt and pretty much shut down all API plays. I ended up shutting down my 3rd party app then but not sure what's their API limits now. Twitter recently made huge changes to their API limits too which impacted a lot of 3rd party apps.
On the note of Twitter's restriction of API usage, Jack talked about it recently on the podcast Tales from the Crypt [0]. He doesn't give any specifics but attributes Twitters early struggle with uptime to unrestricted API usage [1].
Jack has proven himself a liar many times with his false promises regarding taking care of the abuse problem on his platform without success so I’d take anything he says with a pinch of salt.
Let’s also not forget that they have a vendetta against third-party clients (so they can push their own client with the bullshit algorithmic timeline and ads) so it wouldn’t surprise me that he says that just as an excuse. In reality their web access was just as unrestricted as their API so it should share some of the blame too.
I hope Unsplash doesn't end up similar to those.