Easy example. Have they fixed file upload behavior yet? Do they store the entire file in memory by default instead of chunking it and storing it as it comes in?

Are you in 1995? PHP dynamically decides how to manage uploaded files, it will generally store a few MB on RAM and move it to disk after that point. It also support streams so the backend can take the incoming data live and do stuff with it without storing it first as usual in the classical model. There are also plenty of higher level solutions to deal with chunked uploads, mobile clients disconnecting such as https://tus.io/ that are used by large companies like Vimeo.