Is there a reason why status checks applied to a commit don't pull through to the PR status checks?

Hello there,

Is there a reason why status checks applied to a particular commit (from an external scanning tool for example) as part of a PR don't correctly carry up into the live PR for that branch? I can run ADO Pipeline Builds and they appear as expected, and even POST a PR status check back so it appears in the checks section, but it seems very odd that i may have X commit failing with external status checks and it not be visible/shown on the PR itself. In GitHub/Bitbucket it showcases everything in the PR view for related commits.

Any advice greatly appreciated!