The “weight” or stiffness of a Böhm type mechanism has little to do with design or make or even quality (provided not downright badly made) or price. It is primarily to do with set-up, most specifically the weighting of the springs, which can be adjusted. Sure, the mechanism should not be sloppy due to damage or ill-adjustment, nor should it be sticky due to oil in the axles having gone gloopy (a routine maintenance issue), but assuming all else is as it should be, look to the springs.
Beginner/student level flutes tend to be fairly stiffly sprung ex-factory, presumably because they’re expected to be played heavy-handedly, and when it comes to maintenance different woodwind technicians have their own ideas about what constitutes appropriate, or light/medium/heavy key response. You do not have to stick with the as-made spring weighting if it doesn’t suit you! I’ve had a flute overhauled by a well-known, reputable technician which came back so heavily sprung that playing it was like stirring concrete, even though I’d requested as-light-as-feasible springing. I had to readjust the springing myself. I don’t have experience of higher end modern Böhm flutes, so don’t know how different brands tend to set them up, but I do know that most of the now many Rudall Carte Böhm (and related) system flutes I’ve handled which didn’t seem to have been meddled with significantly in their life histories were not at all “heavy” in terms of their action/springing.
For myself I like a mechanism which is adjusted as light as possible to maintain a fairly even “feel” between single action open-standing keys and multiple action ones where linkages mean you are playing “against” two or three springs combined. Closed-standing keys are necessarily more heavily sprung, but still should be no stiffer than required to close them reliably, which can be pretty light if the adjustment/set-up/action is spot on.
That goes also for simple system flutes. I’ve met/played keyed flutes by reputable modern makers which were (clearly as made/sold) so heavily sprung as to make the keys virtually unusable! I have re-set-up several in that respect! I believe the logic may have been, “most players won’t use them and if they’re (usably!) lightly sprung they’re too easy to make leak by accident (leading to complaints), so make 'em stiff…”, though heavy springing of closed-standing keys can also cover for less than well done padding and rough pad seats etc.
One caveat to very lightly sprung set-ups on Böhm flutes - they do tend to sound a bit more rattly and key-slappy than if more heavily sprung, but if you want fast response and play light-fingeredly, it’s much preferable.
If I was buying a higher level new Böhm flute from a reputable music shop and I made a choice which I liked for its sound but thought the action too stiff, I’d insist on them having their technician lighten the action before completing the purchase. With beginner level instruments at the prices they sell for, they’d probably tend not to be willing to accommodate such finickiness (though if you don’t ask, you don’t get), but with anything more expensive, they damn well ought to!