Backport function picks up individual commits instead of using squash/merge commit

[karenzone]

The @jarvis backport command didn't work as I expected.
Disclaimer: Could be user error or that I have an inaccurate mental model.

Case: elastic/logstash#11715
I got my local copy in a questionable state, and so I squash/merged into master from github.: elastic/logstash@34ee17b

I did: @jarvis backport https://github.com/elastic/logstash/pull/11715 7.x 7.8 7.7
I expected the single squash/merged commit to be backported.
Instead, the commits were backported individually.

Is Jarvis expecting the commit instead of the PR perhaps?
@jarvis backport 34ee17b0bfc89816f1d968bae07f2c2f7e081b14 7.x is 7.8 7.7