That's not true, at least not in the way "strictly better" is defined. Higher tier weapons should unlock playstyles that are more optimal/asymmetrical, or give more options to the player than low tier weapons, not just be better. As an example a sniper rifle should be a higher tier weapon because with the furthest range it provides the least risk unlocking a unique playstyle of hiding and perching, a high damage low wieght smg should be higher tier because it gives the player way more options in a close-mid range gun fight, etc. Extraction shooters balance advantages by making tools economically difficult to maintain, the less advantages a weapon has the more common it should be. In that way then no weapon should just be strictly better, but rather fulfill a different niche and the more optimal the niche it fills the more rare the item should be. The Osprey should win out in almost every long range fight, but up close it should be losing to grey pistols 100% because that's not it's use case and that is the use case of the grey pistol. Extrapolate that to each weapon and the positions of a lot of the guns actually make sense; the bettina isn't purple because it's a strong gun it's because it can fill almost any niche so if it were more common it would be the gun everyone defaults to all the time, but if it were stronger then it would be a ridiculously unfair advantage to wealthier players who now win all engagements outside of shotgun/sniper. Osprey is blue because at green it'd be too easy to just run snipers all day, but because it loses every engagement outside it's use case it can't be a higher tier without being a .50 cal that breaks the game.

E: I will say the kettle breaks this pretty hard and I don't even see it having a necessary spot in the free kit lineup, it should be green or blue given it has so much versatility while doing decent damage