I've downloaded the French language pack from sw.pega.com. In the package (115510_FLP7.3.zip) there is a documentation folder and in this folder there is a Readme.txt (Sorry, I meant "Readme" and not "Release Note" in my first post). That's where I found those instructions. I've attached the file for your reference.
BUG-327033French Language Pack 7.3 ReadMe contains refs to DL files instead of HFixes
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Note the question that I asked in my bug report about the class of product (product family) that Pega Language Packs belong to related to the exceptional use of DL file references. The exception is also noted in the Pega-internal SA Style Guide.