Clarification on the expected hierarchy of opam repositories


The documentation page about repositories at

reads that an opam repositories “respect” a certain hierarchy but I recently found an opam repository (the one for grew, mentioned in installation · Grew) which doesn’t entirely comply with it and opam’s CLI doesn’t seem to care (I could add grew’s repository and even install from it without as much as a warning).

The main difference with the specification that I could notice within my local cache at ~/.opam/repo/grew/ was the lack of an intermediate per-package directory grouping all versions of a same package together. Instead, grew-1.6.3, grew-1.6.2, etc. for instance are all direct sub-folders of /packages/.

What modal from RFC 2119 is implied on the page above regarding the “respect” of the documented hierarchy ? Can support for this less restrictive structure be expected to be
maintained and perhaps become official and documented or could we fear for it to be dropped eventually ? Should opam-compatible software be able to handle a wider range of folder layouts ? Can we expect packages to be nested arbitrarily shallow or deep under /packages/ ?