homebrew-bundle: brew bundle install not updating out of date casks

I noticed recently that running brew update and brew bundle install will not update some casks, even though they are outdated.

Using the following Brewfile:

tap "adoptopenjdk/openjdk"
tap "homebrew/bundle"
tap "homebrew/cask"
tap "homebrew/core"
cask "adoptopenjdk/openjdk/adoptopenjdk11"
cask "adoptopenjdk/openjdk/adoptopenjdk8"

yields:

$ brew tap
adoptopenjdk/openjdk
homebrew/bundle
homebrew/cask
homebrew/core
$ brew update
Already up-to-date.
$ brew bundle install
Using homebrew/cask
Using adoptopenjdk/openjdk
Using adoptopenjdk/openjdk/adoptopenjdk8
Using adoptopenjdk/openjdk/adoptopenjdk11
Homebrew Bundle complete! 2 Brewfile dependencies now installed.

When trying to confirm the veracity of this, the following comes to light:

$ brew bundle check --verbose
The Brewfile's dependencies are satisfied.
$ brew cask outdated
adoptopenjdk11 (11,0.3:7) != 11.0.4,11
adoptopenjdk8 (8,212:b03) != 8,222:b10

Which is confirmed when inspecting the casks in question:

$ brew cask info adoptopenjdk/openjdk/adoptopenjdk8
adoptopenjdk8: 8,222:b10
https://adoptopenjdk.net/
/usr/local/Caskroom/adoptopenjdk8/8,212:b03 (97.7MB)
From: https://github.com/adoptopenjdk/homebrew-openjdk/blob/master/Casks/adoptopenjdk8.rb
==> Name
AdoptOpenJDK 8
==> Artifacts
OpenJDK8U-jdk_x64_mac_hotspot_8u222b10.pkg (Pkg)
$ brew cask info adoptopenjdk/openjdk/adoptopenjdk11
adoptopenjdk11: 11.0.4,11
https://adoptopenjdk.net/
/usr/local/Caskroom/adoptopenjdk11/11,0.3:7 (181.4MB)
From: https://github.com/adoptopenjdk/homebrew-openjdk/blob/master/Casks/adoptopenjdk11.rb
==> Name
AdoptOpenJDK 11
==> Artifacts
OpenJDK11U-jdk_x64_mac_hotspot_11.0.4_11.pkg (Pkg)

I would have thought that /lib/bundle/cask_installer.rb#L62 applied here and would have correctly identified the outdated casks as per brew cask outdated? Did I take a wrong turn somewhere?