I think of BOXY as an 80s stationery designer’s playground. The brand was started in 1975 (!) targeting the taste of school boys with colorful spring loaded ballpoints that could be used to launch equally colorful sports car erasers for desktop races.
So, unless a BOXY pen is obviously sporting some metal construction, I’d just lower my expectations. You are indeed correct that the all plastic M5-330 W-Knock isn’t all that great of an experience. It feels a bit squeaky and ‘hollow’ but their original target audience wouldn’t have cared. THE STICK fares better in that it is a basic clicker MP. The clutch and feel are pretty normal. In BOXY land, FORM ≥ FUNCTION