By default, using --numprocesses will send pending tests to any worker that is available, without any guaranteed order. You can change the test distribution algorithm this with the --dist option. It takes these values:

--dist no: The default algorithm, distributing one test at a time.
--dist loadscope: Tests are grouped by module for test functions and by class for test methods. Groups are distributed to available workers as whole units. This guarantees that all tests in a group run in the same process. This can be useful if you have expensive module-level or class-level fixtures. Grouping by class takes priority over grouping by module.
--dist loadfile: Tests are grouped by their containing file. Groups are distributed to available workers as whole units. This guarantees that all tests in a file run in the same worker.

Но я так понял, не совсем поможет именно в моем случае.
Разделение по модулю и файлу.
Мне нужно именно по директориям.
Но погулю и так, спасибос

Ты можешь как угодно раскидывать, как раз в 10ом пункте пина пример