Why isn't addons_contribmodule in sys.path? (2.90)

From reading the manual, I’m assuming that the proper place to put my own scripts and modules (in Windows) is
%USERPROFILE%AppDataRoamingBlender FoundationBlender2.90scriptsaddons_contribmodule

According to the Blender 2.90 (and I think earlier) manual, it sounds like the path should automatically be added to sys.path:

./scripts/addons_contrib/modules/*.py

Modules for addons_contrib to use (added to Python’s sys.path).

But according to the Python console, it isn’t (addons_contrib is, but addons_contribmodules isn’t).

Am I misinterpreting something?