I can see how this can be confusing as the title says 6.3 and there is note that says “This dictionary contains the warnings for PRPC 6.3.”.
However at the bottom, it does show the versions7.1.1 - 7.4. Those are the range, so any version of Pega between 7.1.1 and 7.4 (which would include 7.1.9 yes).
I reached out to my colleagues on the Pega Community KnowledgeBase side and found out that since this article is archived, we are not updating the versioning but it does include 7.1.9 in that range.