It does - near absolutely nothing - it changes the ram priority with which the worker process that builds things is created.
Its the same as opening task manager and changing priority to that specific exe.
Chanches of that being an issue off a direct build command are next to nhil, however with just how badly the engine is coded of late, you never really know until you try.
And if for whatever reason you absolutely need that worthless minimap that should just always be closed so you can actually work… well, then trying that setting is worth a shot.