https://ftp.drupal.org/files/projects/bootstrap4-2.1.6.zip contains vrong branch

Problem/Motivation

composer.lock has the next lines

"name": "drupal/bootstrap4",
            "version": "2.1.6",
            "source": {
                "type": "git",
                "url": "https://git.drupalcode.org/project/bootstrap4.git",
                "reference": "2.1.6"
            },
            "dist": {
                "type": "zip",
                "url": "https://ftp.drupal.org/files/projects/bootstrap4-2.1.6.zip",
                "reference": "2.1.6",
                "shasum": "7eb8d2f3409db97a2b55f46f22a6ef59596a25a7"
            },

but https://ftp.drupal.org/files/projects/bootstrap4-2.1.6.zip contains code from another branch.

Steps to reproduce

composer require "drupal/bootstrap4"

Solution use --prefer-source. but this is quite slow