I generally think that is true but sometimes it feels like the user, me included, may try to use a specific piece 'out of spec'. I bought an EVO last fall and ended up with a Large Tall because it fit over an Ambient hoodie better than a regular Large, with more under-arm space. I guess in that way, it is not intended to fit over that piece in a 'like' size?? Over a Large heavyweight hoodie, no problem really. The XL for me was definitely more loose, but too loose without an underlayer. So I went LT.
When I bought my Stratus set I ignored online research and still bought an XL instead of a Large and while it fits fine enough and layers easily, I sometimes get annoyed that in mild temps, it's a big baggy. That's on me. I would prefer Sitka do one simple thing.... normalize/standardize their 'ratings' of wind/water/warmth/durability etc. They're still all over the place with those categories and it's really hard to get a straight comparison at times and would be much easier if EVERY piece had the same categories, even if one or two are zero rating, be consistent!