Yep, docks are known not to request 4 lanes for DP even when there's only a display plugged in. In fact even dongles that don't have anything other than a display output on them sometimes only ever request 2 lanes, sadly.
You can't really blame them, though. The vast, vast majority of users will be absolutely fine with 2 lanes, especially with DP 1.3+. USB C is mainly used on laptops, and your office projector just isn't going to support 8K120 with HDR. Why spent the extra money if virtually nobody needs it?
