Weak but enabled dependency isn't included in graph

[MarijnS95]

Describe the bug
Since cargo-deny 0.13.2, which upgraded to krates 0.12.3 we get a strange warning on our repo:

warning[license-exception-not-encountered]: license exception was not encountered
  ┌─ laz-license-repro/deny.toml:8:14
  │
8 │     { name = "laz", allow = ["LGPL-2.1"] },
  │              ^^^^^ unmatched license exception

The laz crate is optional=true included via las, but we enable that feature unconditionally and expect laz to be part of the crate graph:

las = { version = "0.7", features = ["laz"] }

To Reproduce
Steps to reproduce the behavior:

Take this Cargo.toml:

[package]
name = "laz-license-repro"
version = "0.1.0"
license = "Apache-2.0"

[dependencies]
# laz = "0.6"
las = { version = "0.7", features = ["laz"] }

And this deny.toml:

[licenses]
allow = [
    "MIT",
    "Apache-2.0",
    "Unicode-DFS-2016",
]
exceptions = [
    { name = "laz", allow = ["LGPL-2.1"] },
]

[[licenses.clarify]]
name = "laz"
expression = "LGPL-2.1"
license-files = [
    # bonus: this crate states `license-file = "COPYING"` but `cargo-deny` insists on using `LICENSE.txt`?
    # { path = "COPYING", hash = 0xc5199cf9 },
    { path = "LICENSE.txt", hash = 0xc5199cf9 },
]

Run cargo-deny and observe:

$ cargo deny check license
warning[license-exception-not-encountered]: license exception was not encountered
  ┌─ laz-license-repro/deny.toml:8:14
  │
8 │     { name = "laz", allow = ["LGPL-2.1"] },
  │              ^^^^^ unmatched license exception

licenses ok

Expected behavior
No warnings. And when laz would be removed from license.exceptions cargo-deny must complain about LGPL-2.1 not being allowed.

Device:

• OS: Linux
• Version: Cargo deny 0.13.2 and up

Additional context
Feel free to uncomment # laz = "0.6" and observe what cargo-deny output we expect when this crate is definitely part of the graph. For example, without the license.clarify cargo-deny rightfully complains about error[unlicensed]: laz = 0.6.4 is unlicensed but it doesn't do that anymore when the crate is transitively included via las = { version = "0.7", features = ["laz"] }.