I gave 11.11.5 as an example. The upgrade path for you would be:
13.1.11 → latest
13.12.Z → latest
14.1.Z → latest
So if you are on 11.11.0 or 11.11.5 or something in between, you would need to upgrade to 11.11.8 before continuing to the next version. But this is when doing Gitlab CE → CE upgrades to get from your current version to the latest version.
If you want to do Gitlab-CE to Gitlab-EE then you must install the same Gitlab version as the Gitlab CE version currently installed. So if your system has Gitlab-CE 11.11.0 then you need to install Gitlab-EE 11.11.0.
The upgrade path is something different than upgrading between CE and EE. If you were on the latest Gitlab-CE 14.1.2, then you would install Gitlab-EE 14.1.2 to move from CE to EE.
Also, you can once on Gitlab EE then follow the upgrade path to get to the latest Gitlab EE release, the procedure for upgrading from current to latest release is the same, and the same upgrade path would need to be taken.
So don’t confuse the upgrade path, with moving from CE to EE.
The docs are also in CE form as well: GitLab Docs | GitLab just changing EE in the URL like this URL has.