opam install --deps-only skips the installation reasons

[avsm]

With opam 2.1beta5, opam install . shows the reason a package is included.

$ opam install .            
Package base-images does not exist, create as a NEW package? [Y/n] y
base-images is now pinned to git+file:///Users/avsm/src/git/ocurrent/docker-base-images#nnpchecker (version ~dev)
The following actions will be performed:
  ∗ install seq                     base         [required by re, fmt, tyxml]
  ∗ install conf-m4                 1            [required by ocamlfind]
  ∗ install conf-gmp                3            [required by zarith]
  ∗ install mirage-no-xen           1            [required by mirage-crypto-pk, nocrypto]
  ∗ install conf-capnproto          1            [required by capnp-rpc-net]
  ∗ install camlp4                  4.10+system  [required by extunix]
  ∗ install ocamlbuild              0.14.0       [required by extunix, astring, bos]
  ∗ install conf-pkg-config         2            [required by mirage-crypto]
  ∗ install dune                    2.8.2        [required by base-images]
  ∗ install mirage-no-solo5         1            [required by mirage-crypto-pk, nocrypto]
  ∗ install cmdliner                1.0.4        [required by current_github, capnp-rpc-unix, dockerfile-opam]
  ∗ install jbuilder                1.0+beta20.2 [required by irmin-watcher]
  ∗ install conf-which              1            [required by conf-graphviz]
  ∗ install ocamlfind               1.8.1        [required by extunix, astring, bos]
  ∗ install conf-gmp-powm-sec       3            [required by mirage-crypto-pk]

But opam install . --deps-only does not

The following actions will be performed:
  ∗ install seq                     base
  ∗ install conf-m4                 1
  ∗ install conf-gmp                3
  ∗ install mirage-no-xen           1
  ∗ install conf-capnproto          1
  ∗ install camlp4                  4.10+system
  ∗ install ocamlbuild              0.14.0
  ∗ install conf-pkg-config         2
  ∗ install dune                    2.8.2
  ∗ install mirage-no-solo5         1
  ∗ install cmdliner                1.0.4
  ∗ install jbuilder                1.0+beta20.2
  ∗ install conf-which              1
  ∗ install ocamlfind               1.8.1
  ∗ install conf-gmp-powm-sec       3
  ∗ install uchar                   0.0.2
  ∗ install conf-sqlite3            1
  ∗ install stdlib-shims            0.3.0
  ∗ install stdint                  0.7.0
  ∗ install sexplib0                v0.14.0

It would be handy to always see the installation reason, irrespective of if the local packages are being installed or not.
(Severity of this is minor, not a blocker for anything)

[AltGr]

My guess is that the reasons are computed from the requested packages ; in the case of deps-only these were removed from the list before the printing, and without a root to start from, the whole "reasons" computing is skipped.