obviously your not paying attention
I am fully aware a 4wt switch is not the same as a 4wt single however it IS NOT the equivalent of a 7wt single as you eluded to earlier !
I think the reason people may think this way is because of how fly lines work in regards to using single handed lines for two handed rods. two handed rods need higher grain weights to load properly
Two hander - single handed lines
4wt - 7wt
5wt - 8wt
6wt - 9wt
and so on. of course this is not an exact science but its a place to start when trying to match single handed lines to a two handed rod (usually switches)
Im not sure exactly how they figure out line weights for rods but im sure it has something to do with breaking strength, blank thickness.........etc.
im sure if you were to google your 4wt switch or a 4wt spey it will say they are recommended for fish up to 5lbs (maybe even smaller!!) of course we all know they can handle more weight but to say they are a good match for salmon is just an unethical thing to say especially talking to a newbie fisher/fly fisher. They will not have the skills to control large fish on light tackle and therefore be tiring fish out to the point of death or breaking their tackle costing them money and frustration.
feel free to continue using your 4wt switch for coho because obviously nothing that is said will change your mind. I just dont like seeing people suggest tackle that is too light for the species they are targetting.
HOOK - has used a 5wt for Squamish pinks many times however now has a 5/6 switch to use instead. Wait ! will i even feel them on it ?