Winter just means specc’d appropriately, normally slightly bigger tyres, full guards and if you have any sense either rims with a thicker sidewall for longevity or discs, and possibly gearing ratio changes if you’re going to be riding solo more often or carrying more weight (clothing, food, bike weight etc.)
Doesn’t have to mean you skimp on the frame or group though, although I’m a bit partial to running older (but decent) 7/8 or 9 speed groups as they do deal with the crap a bit better, and in my experience they do last longer, but others may have different experiences.
I use my ‘winter’ bikes all year round as they’re great for loads of riding, I just don’t ride my un-guarded, lightweight/thin rimmed wheels, highly geared bike in crap weather, not because it’s too good for bad weather, but because the other bikes are better equipped for it.