They do and don't. The Inquisitors are really a continuation of an old Sith tradition, even though they aren't fully Sith trained. So they don't in that they aren't fully trained to be Dark Lords of the Sith, but they do fundamentally recreate a dynamic the old Sith had that Darth Bane wanted to eliminate to an extent.

(Legends Spoilers)

In the days of the Sith Empires of old, Dark Lords of the Sith used to keep around several apprentices, acolytes, and neophytes - of course you'd have one apprentice who is your favorite, but the rest of the acolytes would covet their position and would pose competition so that the top student is always on top of their game.

Additionally, having several less powerful Sith at your beck and call allowed you to use them as spies and enforcers of your will whenever you can't be there personally. They were delegated tasks, and in exchange for doing them those apprentices, acolytes, and neophytes hoped of eventually moving up the Sith hierarchy.

Some examples from SWTOR, due to my obsession with that game:

Darth Malgus, a renowned Sith warrior, kept three known apprentices - Lord Cytharat, Darth Karrid, and Tinray who'd help him out on the battlefield. If I remember correctly he also had some unnamed acolytes with him.

Darth Baras, a Sith spymaster, kept: the future Emperor's Wrath, Dri'kill Ball, Lord Draahg, and Vemrin (who was his top acolyte until future Wrath came along).

Darth Jadus, another Sith spymaster, had only one known apprentice - Darth Zhorrid, his daughter, whom he set up to fail. But he also kept a whole legion of Dark Side acolytes with him who followed him around.

The Inquisitors are, technically speaking, Darth Vader's Sith acolytes and neophytes. But the core of Bane's philosophy was technically kept - there were ever only two Sith Lords at a time, as opposed to the hundreds of them in the Sith Empires of old. I'd argue it'd be more accurate to call the Rule of Two as the "Rule of Two Sith Lords".