Earlier quoted context omitted.
If it works in vim it should work in neovim?
It was forked before vim 8.0 was released and neovim doesn't try to keep its fork compatible with vim. Consequently it is not.
Nvim tracks all Vim patches[1]. _Only_ the job-control API differs. All other Vim patches are merged into Nvim reguarly, including new Vimscript features like partials, lambdas, etc.
Nearly all 7.4.x patches (except for job-control) have been merged:
https://neovim.io/doc/reports/vimpatch/
Hundreds of 8.0.x patches have been merged also, but they won't be in that report until we finish the last couple 7.4.x patches.
[1] https://github.com/neovim/neovim/wiki/Merging-patches-from-u...