Some PR's I can't find pull request title in git merge commit body

pull request merge commit is usually this shape

commit 6e80b4ba2c45915bc20240344aa674a0eb99698b
Merge: 4d05e8c 42071ac
Author: giichiro.sasaki <giichirosasaki@users.noreply.github.com>
Date:   Wed Jun 30 13:13:41 2021 +0900

    Merge pull request #1 from giichirosasaki/pr-1

    pr1, aaaaaaaaaa  <-  'PR title'

but some merge commit hasn’t ‘PR title’ .

commit 27936b94bdb4fcb64043dde901e8c07c6ce2eea7
Merge: 7d8e4f411 3e3034cc0
Author: giichiro.sasaki <giichirosasaki@users.noreply.github.com>
Date:   Tue Jun 29 18:11:16 2021 +0900

    Merge pull request #8113 from giichirosasaki/hotfix/issue_7803

When is the ‘PR title’ not included?

that PR title included characters # , .
Maybe there are prohibited characters in PR?