Don’t rename functions or file basenames without good reason
Including individual files is out of scope for math lib API support as laid out by @seantalts (see point 1).
I believe point 2 in the supported API doc lays out that no functions will ever change name or argument structure within those meta-headers. So I think changing the name of a function violated that rule.
Going forward, RStan’s going to need to stop including files on an ad hoc basis and get what it needs included in the bigger headers.
P.S. There’s already a huge Discourse topic on what should be supported..